Milan, San Lorenzo
Professor Dale Kinney
San Lorenzo in Milan is an enigma. It is a daring building on
a grand scale, much admired by Renaissance architects and especially
by Bramante, whose design for the dome of St. Peter's shows
its influence, as does the closely related pilgrimage church
of Santa Maria della Consolazione at Todi (1508). Yet modern
architectural historians tend to disparage it as not-quite-great.
Despite the fact that it may be the earliest known example of
its type (the "aisled tetraconch"), W.E. Kleinbauer
calls it "a derivative building". Moreover, no one
in late antiquity wrote its history, so we have no documentary
evidence of when it was built, why, or for whom. The origins
of San Lorenzo remain one of the great unsolved mysteries of
early Christian architecture.
San Lorenzo is the centerpiece of a complex of buildings erected
outside the Roman wall of Milan - though well inside the modern
city - aligned with the ancient road to Pavia. It was separated
from the road by an atrium fronted by a grand colonnade of sixteen
fluted Corinthian columns, second-century in style and therefore
reused from an earlier building. Smaller buildings are attached
to the main church on the east-west and north-south axes: the
small niched octagon of San Sisto on the north; Sant'Ippolito,
a larger octagon with a cruciform interior, on the east; and
the still larger octagon of Sant'Aquilino, identical in plan
to San Sisto, on the south.
San Lorenzo itself has a symmetrical, four-lobed shape called
a "tetraconch", from the Greek words for "four"
and "shell [conch]". Geometrically it is a square
whose sides curve outward to make the four "lobes".
In San Lorenzo, the corners of the square are exaggerated to
become towers, which appear on the plan as four small squares
between the curved walls. The four-lobed perimeter is echoed
internally by curved colonnades anchored by four piers. This
type of design, in which the outer wall is doubled inside by
another enclosure, is called a "double-shell". Double-shell
designs seem to have been a late antique invention; the first
clear example is Santa Costanza in Rome, built as a mausoleum
in the middle or second half of the fourth century. Santa Costanza
has a circular outer wall and a circular interior colonnade.
Double-shells are also frequently octagonal, like San Vitale
in Ravenna of the sixth century. Double-shells flourished in
the fourth through sixth centuries, then became rare. They are
in the genealogy of the unique design of Hagia Sophia, which
maximizes double-shell principles and applies them to the longitudinal
layout of a basilica.
The double shell design moves the load-bearing function of the
outer walls to the inner "shell" of supports. This
favors structural efficiency by decreasing the span of the dome
or vault over the center, and making it possible to concentrate
the weight of the superstructure on a few relatively massive
supports (the four piers in San Lorenzo), which can be buttressed
if necessary in the space between inner and outer shells. In
San Vitale, the eight piers that mark the inner octagon carry
the dome by themselves, but in San Lorenzo the four piers that
carry the superstructure are joined to four towers in the spaces
between the four "conches" of the plan. Depending
on the form of the vault, the towers may have had a buttressing
function, in addition to housing the stairwells that provided
transit between the first and second levels of the ambulatory.
Today the central space is covered by a tall ribbed dome that
was designed by the architect Martino Bassi after a prior dome
collapsed in 1573. It dominates the exterior view of San Lorenzo
and gives it a verticality that is probably quite unlike the
Below the dome, the exterior still shows much original fabric.
The original masonry employs the characteristic Lombard brick,
thicker and shorter than bricks used in Rome, and deep red in
color. The thin-walled perimeter of the tetraconch probably
is of this masonry, now covered by stucco, and it is plainly
visible on the towers and chapels. The best-preserved tower
is the northeast one, which retains most of its early Christian
fenestration; the others have been cut down (northwest), given
typical Romanesque slit windows (southeast), or conversely,
opened up at the top with a loggia for bells (southwest). The
best-preserved chapel is Sant'Aquilino, which is unchanged including
its dome, except for the exterior "dwarf gallery",
where the original columns have been replaced by thin brick
The interior elevation of San Lorenzo does not survive except
in outline. The stone piers at the corners of the central space
are connected by two-storied colonnades with ambulatories behind
them. No two of these two-storied colonnades are alike; some
have masonry columns or piers; one has monolithic columns; most
are arcaded but one has a horizontal trabeation, etc. The general
appearance of the inner shell comes from the late 16th century,
but the colonnades may have been partially rebuilt before then
as well. We might imagine that originally all of the colonnades
on both stories were composed of monolithic marble columns and
marble capitals (probably all spolia) and that all were arcaded,
like the interior of San Vitale. San Lorenzo had much broader
proportions than San Vitale, however, and a more expansive effect,
not only because it was four-sided rather than octagonal but
because it is significantly larger. Its north-south clear width
is 47.9 m. The interior square is 24 m. on a side, and also
24 m. high.
The arcades must have been damaged in the major fires that devastated
Milan in the middle ages and in the two known collapses of its
dome. Two fires are documented between 1070 and 1075, and another
in 1123 or 1124. In this period there was unquestionably some
rebuilding. A drawing made ca. 1573 purports to show the dome
as it existed before the collapse of that year; there has been
some debate about whether it shows the original vaulting, repaired
in the 11th-12th centuries, or a totally Romanesque replacement.
A dome 25 m. in diameter would have been a major feat for Romanesque
builders; on the other hand, it is questionable that the original
late Roman designers would have projected a dome over this square
base. The presence of corner towers has suggested to some that
the original covering was a masonry groined vault springing
from the four corners; still others have proposed a low wooden
In the absence of documentation, historians have looked to circumstantial
evidence to date San Lorenzo. A massive stone platform (platea)
under the vestibule and part of the octagon of Sant'Aquilino
contains molded and profiled blocks which seem to have come
from a partial dismantling of the nearby Roman amphitheater.
Thus for some scholars, an event alleged to have occurred in
the amphitheater in 396 marks the earliest possible date for
San Lorenzo; others point to an edict prohibiting gladiatorial
combats of 405, which would have made the amphitheater obsolete;
still others point to the removal of the imperial court from
Milan to Ravenna in 408. San Lorenzo's grandiose colonnaded
entrance, the scale and complexity of its design, and the probable
funerary use of the smaller buildings attached to it make imperial
patronage more plausible than construction by a bishop, especially
in the later fifth century when Milan was beset by repeated
incursions of "barbarians".
The fact remains, however, that we do not know who built San
Lorenzo, or for what purpose. Although I myself have argued
for a dating in the third quarter of the fourth century, I no
longer believe that it is possible to be so conclusive. There
is evidence for and against every possible date between ca.
350 and ca. 410. The architect Roberto Cecchi drew attention
to an important consideration that others have overlooked, namely
the use of ribs of hollow clay tubes (tubi fittili) in the vault
of Sant' Aquilino. Tubi fittili were used to much better effect
in Ravenna, where a dome of clay tubes was daringly inserted
over the Orthodox Baptistery ca. 450, and in the larger dome
of San Vitale ca. 540. Cecchi infers that the San Lorenzo complex
represents a prior phase of experimentation with this innovative
structural material, which he would date around 400.
We are equally unclear about San Lorenzo's purpose and function.
Even the original dedication is not known for sure, although
the dedication to St. Lawrence (=Lorenzo) does go back at least
to the fifth century, when the cult of this Roman deacon (martyred
in the third century) was very popular. It is not known how
the original building functioned liturgically, or where the
altar stood. Today the altar is on a platform in front of the
eastern interior colonnade, but there is no good evidence that
it stood there originally, or even that there was an altar at
all. The location of the complex outside the city walls is evidence
that it had a funerary purpose (since burial within the walls
was forbidden), and the small chapel of San Sisto definitely
was built as a tomb by Bishop Lawrence I (d. ca. 500). San Sisto
is a later addition to San Lorenzo, as indicated by the fact
that its masonry is not in bond with the main building. Sant'Aquilino,
which is original, has the shape of contemporary mausolea and
baptisteries. Most scholars think that Sant' Aquilino was meant
to be the tomb of the founder or founders of San Lorenzo, whoever
they might have been.
San Lorenzo is the only fully standing example of the double-shell,
or aisled tetraconch. Twenty-one other examples have been identified
in ruins, including one in Italy, at Canosa in Apulia. The others
are in Greece, the Balkans, Egypt, Syria, Armenia, and ancient
Mesopotamia. None of these ruins seems to date earlier than
ca. 400 CE. A number of scholars have tried to identify the
origin of the tetraconch as a type (Kleinbauer, using terminology
first applied by Richard Krautheimer to the early Christian
basilica, calls it a genus); usually the postulated prototype
is Constantinian. One hypothesis is that the first tetraconch
was the cathedral of Antioch, destroyed in the early middle
ages, which is referred to in certain sources as the "Golden
Octagon". Kleinbauer, who once supported this hypothesis,
now argues instead that the prototype was a church in Constantinople.
All such proposals are speculative and incapable of proof one
way or the other. It might be more fruitful to focus on the
distribution and function of the known examples; for example,
Kleinbauer's recent study of the tetraconch in Athens highlights
the probable civic prominence of this substantial building erected
around the same time as San Lorenzo, in the repaired court of
the Library of Hadrian.
One of the most pleasing effects of the double-shell design
is to diversify the interior domed or vaulted space. Compared
to the undifferentiated expanse under the dome of the Pantheon,
for example, the interior of San Lorenzo offers contrasting
experiences of open continuous space in the center and bounded,
contoured and interrupted spaces behind the internal colonnades.
When the enveloping spaces between outer and inner shells are
double-storied the design also offers multiple elevations, as
in San Lorenzo, with its gallery above the ground-level ambulatory.
Multiple elevations create multiple and diverse viewing positions.
While in the Pantheon the only viewpoints are from within the
domed center and directed upward, San Lorenzo offers views into
the center space from outside it, downward from the gallery
as well as upward from the ambulatory. The centralized double-shell
is thus a highly spectatorial space, and also an auditorial
one. The design brings more people closer to the presumed focal
point than the longitudinal basilica, making it possible for
more people to see and hear clearly whatever is happening there.
Nevertheless, it was the basilica that won out in the west as
the standard form of church building, perhaps because it was
easier to build, and perhaps also precisely because of the tetraconch's
relatively more egalitarian character, which was counter to
the tendency to make the Christian liturgy progressively more
hierarchical and hieratic.
W. Eugene Kleinbauer, "Christian or Secular? The Tetraconch
in the So-called Library of Hadrian at Athens", in Nova
Doctrina Vetusque. Essays on Early Christianity in Honor of
Fredric W. Schlatter, S.J., eds. Douglas Kries and Catherine
Brown Tkacz (New York: Peter Lang, 1999), 203224.
Dale Kinney, "Le chiese paleocristiane di Mediolanum",
in Il Millennio ambrosiano. Milano, una capitale da Ambrogio
ai Carolingi, ed. Carlo Bertelli (Milan: Electa, 1987).
W. Eugene Kleinbauer, "The Double-Shell Tetraconch Building
at Perge in Pamphylia and the Origin of the Architectural Genus",
Dumbarton Oaks Papers 41 (1987), 277293.
La Basilica di San Lorenzo in Milano, ed. Gian Alberto
Dell'Acqua (Milan: Banca Popolare di Milano, 1985), esp. Roberto
Cecchi, "Architettura. Alcuni momenti costruttivi",
Richard Krautheimer, Three Christian Capitals. Topography
and Politics (Berkeley & Los Angeles: University of
California Press, 1983), 81-92.
Suzanne Lewis, "S. Lorenzo Revisited: A Theodosian Palace
Church at Milan", Journal of the Society of Architectural
Historians 32 (1973), 197222.
Dale Kinney, "The Evidence for the Dating of San Lorenzo
in Milan", Journal of the Society of Architectural Historians
31 (1972), 92107.
W.E. Kleinbauer, "Toward a Dating of San Lorenzo in Milan",
Arte lombarda 13 (1968), 119.
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