Turin's Portici and Their Role in 18th-Century Commercial Urban Planning

Via Po, Turin — portici photographed circa 1925 by Mario Gabinio. © Wikimedia Commons, public domain

Turin's Urban Grid and the Problem of Continuity

Turin's historic centre is defined by a Roman castrum grid that Savoyard planners systematically extended from the mid-17th century onward. Unlike Bologna, where the portico emerged from ad hoc private construction and was subsequently codified, or Padua, where a single civic building concentrated the arcade function, Turin's portici were instruments of planned urban expansion. They appear in the architectural program of new streets from the outset — specified in building regulations, drawn into elevation studies, and enforced as conditions of the ground leases under which private construction occurred on Savoyard-owned land.

The consequence is a different spatial quality. Turin's portici are uniform in bay width, arch profile, and storey height across entire street frontages. The variation that characterises Bologna's network — a direct record of different builders, different centuries, different materials — is absent. Turin's arcades read as a single architectural decision applied continuously, which is precisely what they were.

Via Po: Design Origins and 1673 Planning

Via Po was laid out as part of Turin's second urban expansion, with planning documented from 1673 under the direction of Amedeo di Castellamonte, court architect to the House of Savoy. The street runs 704 metres from Piazza Castello — the Savoyard dynastic centre — to what was then a military parade ground and is now Piazza Vittorio Veneto. It was Turin's widest avenue at the time of completion, known as the Regina viarum, and it introduced for the first time in Turin a continuous portico on both sides of a straight urban axis.

Before Via Po, covered walkways had appeared in Turin only at piazza level — most notably around Piazza Castello and Piazza San Carlo, where uniform arcade frontages defined the perimeter of civic squares in the manner established by Carlo and Emanuele di Castellamonte in the 1630s. The innovation of Via Po was to extend this continuous arcade along a full street length, creating a covered pedestrian corridor between two major civic spaces.

Architectural Form: Bay Width, Height, and Material

The standard bay of Via Po's portici is approximately 5.5 metres wide with a clear height of around 4 metres at the underside of the arch. This is considerably larger than the medieval portici of Bologna, which average 3–4 metres in both dimensions. The greater scale reflects Turin's planning ambitions — the portico here was intended to accommodate commercial uses of a different character: cafés, bookshops, and later the Galleria Subalpina shopping passage rather than the street vendors and market stalls of the medieval arcade.

Construction material throughout the Via Po portico system is plaster over brick, with stone for pilaster bases and arch keystones. The uniform application of stucco across all surfaces — a Piedmontese Baroque convention — conceals the structural brick behind a rendered finish that could be regularised across the entire street frontage regardless of the different builders who constructed individual sections.

The Commercial Logic of the Covered Street

Via Po's portici were not primarily a weather amenity — though Turin's climate, with significant rainfall and cold winters, made covered passage commercially valuable. Their primary function was to guarantee commercial frontage continuity. A shop under a portico at one end of Via Po could be advertised in terms of its position relative to the covered street as a whole, not merely its individual facade. The arcade created a coherent commercial address system before modern street numbering existed.

By the 18th century, the portici of Via Po housed the densest concentration of commercial activity in the Savoyard capital: booksellers, printers, instrument makers, and the coffee houses where Turin's Enlightenment intellectual life was conducted. The Caffè Al Bicerin, the Caffè San Carlo, and the bookshops clustered around the university entrance on Via Po were all portico-fronted establishments. The covered street functioned as a commercial amplifier — lengthening the hours and weather conditions under which outdoor retail and social activity remained viable.

The 1819 Royal Intervention: Bonsignore's Connecting Terraces

A specific royal intervention in 1819 extended the portico logic in an unusual direction. King Vittorio Emanuele I instructed Ferdinando Bonsignore to design connecting terraces that would allow the king to walk between palaces along Via Po without requiring carriage transport or exposure to rain. The terraces created an elevated covered passage at first-floor level, connecting portico rooftops along sections of the street.

This episode — a private royal promenade built above a public commercial arcade — captures Turin's particular relationship between the Savoyard court and the city's civic infrastructure. The portico was simultaneously public and controlled; a space of commerce and of courtly circulation. The 1819 terraces were eventually dismantled, but Bonsignore's work clarified that the portico system had structural capacity for vertical extension that later 19th-century builders would exploit when adding storeys to Via Po's frontages.

Piazza Castello and the Civic Square Model

The arcades of Piazza Castello, dating from the Castellamonte planning of the 1630s, predate Via Po and establish the spatial model that Via Po extended linearly. The Piazza's continuous arcade runs around three sides of the royal square, connecting the Palazzo Reale, the Palazzo Madama, and the Teatro Regio under a uniform covered perimeter. Movement between these institutions was sheltered and framed by architecture rather than exposed to the street.

The civic square model of Piazza Castello differs from the commercial street model of Via Po in its organisational logic: the square arcade is centripetal, drawing movement inward toward the enclosed civic space, while the street arcade is linear, directing movement along an axis between two terminal points. Turin used both models within the same street grid — a spatial repertoire that Bologna, with its distributed private-obligation system, and Padua, with its single concentrated civic building, did not develop in the same systematic way.

Turin's Portici in Comparative Context

Turin's total arcade frontage across the historic centre exceeds 18 kilometres, placing it among the most extensively arcaded cities in Italy alongside Bologna and Genoa. Unlike Bologna's network, Turin's portici are not under UNESCO inscription as of 2026, though periodic proposals for nomination have been discussed in Italian heritage planning circles since the late 2010s.

The comparison with Bologna highlights the degree to which UNESCO's 2021 inscription rewarded historical continuity and legal documentation as much as architectural quality. Bologna's portici span more construction periods and more structural types; Turin's are architecturally more coherent and spatially more deliberate. Both demonstrate the portico as a fundamental instrument of Italian urban form, applied to different planning conditions with different results.

Last updated: 3 May 2026