City and Summit: Siena, Italy

The city of Siena began as an Etruscan settlement, and—following Etruscan practice—was built on a well-defended hilltop. When the Romans conquered the town, naming it Saena Julia, they seem to have preserved much of the Etruscan structure. Roman Siena consisted of a regular, planned town, and an adjacent fort; their combined purpose was to survey and protect Tuscany. The plateau they shared was high enough to provide observation points, yet flat enough to provide a level plane for the city. Roads extended to the north and south, but were not frequently travelled; they led mainly to three necropolis complexes.

Plan of Saena Julia and its fort, superimposed on modern Siena.

Traffic through Siena increased dramatically in the Middle Ages, when the reorganization of trade routes made Siena a commercial center to rival Florence. A town once constructed to survey the landscape now became a thriving organ along its central artery. Thus Siena's relationship to its landscape changed: the city spread, and its center migrated down from its plateau, coming to rest in the hilly basin through which the Roman road extended. This road, formerly outside the city walls, became the economic axis of the city—it was renamed Via Banchi di Sopra, commemorating the banking industry that came to dominate the street. (Another segment of extramural Roman road became known as Via di Città.) The intersection where the main Roman road branched toward Saena Julia became the outline of medieval Siena's Campo, the shell-shaped piazza that became the city's new center. The heart of Siena thus shifted down from its topographically highest point—the plateau where the Roman forum had stood—to one of its lowest: the basin of the Campo. As Siena became a gathering place for travelers, wealth, and power—as it drew things unto itself—its spatial rhetoric likewise became one of "collecting"—for the Campo is also Siena's largest drain.

Siena, with the Campo in the foreground. The street that cuts through the foreground is the ancient Roman road, leading to Saena Julia.

But the plateau has not been abandoned. The memory of the Roman town is conserved there, in what is now Siena's southwest corner—the buildings do not overstep the footprint of the ancient walls. And to the south, the shape of the fort—which became, in the Middle Ages, the fortified Castelvecchio—is remarkably preserved in the grid of the streetplan. Alongside these preserved "negative images," the plateau of Siena also recalls its past self in terms of function—for on the site of the Roman forum stands Siena's other great gathering place: its cathedral. This substitution conserves a fundamental identity of this place as one of assembly.

But in the 13th century, when the cathedral was built, Siena had already "slid" down from the plateau onto the road. For this reason, the cathedral extends beyond the area of the ancient forum: it pushes beyond it to the north, projecting out over the edge of the plateau. Underneath this projection, the architects inserted the cathedral's baptistry. The effect is this: the cathedral's front sits on the high ground; but the back of the cathedral cascades down the hillside, with the back façade coming to rest at a significantly lower elevation than the front.

Siena Cathedral, with its two façades and the ground levels onto which they open mapped.

Lower façade of the cathedral (entrance to baptistry); note the steps on the left that lead up to the front of the cathedral.

These double façades, the two faces of the cathedral, allow it to unify the plateau with the lower hills beneath; the building spans topographical changes to create a synthetic urban space from a divided landscape. And there might even be a further symbolic meaning: for the baptistry is on the lower level, only slightly raised from the level of the city, while the nave of the cathedral is above. The baptistry can therefore be seen as a sort of "transitional space" between city and church—and this is in fact its function, as it is here that the Sienese are "introduced" into the church by baptism.