Ruelle de paris on Flickr.
Via Flickr:
A sett, usually the plural setts and in some places called a Belgian block,[1] often incorrectly called “cobblestone”, is a broadly rectangular quarried stone used originally for paving roads,[2] today a decorative stone paving used in landscape architecture.[3][4] A sett is distinct from a cobblestone by being quarried or shaped to a regular form, whereas a cobblestone is generally naturally occurring.
Streets paved with setts are highlights in several cycling competitions such as the final Champs-Élysées stage of the Tour de France and the Paris–Roubaix road race as riding upon them is technically more challenging than riding on asphalt[citation needed].
Notable roads paved with setts include Vicars’ Close, Wells,[5] much of Edinburgh’s Royal Mile and the set of Coronation Street.
In New York City the meat-packing district and SoHo retains such streets.
Germantown Avenue in Philadelphia, in particular its upper reaches through Germantown, Mount Airy and Chestnut Hill, is notable for being paved with Belgian blocks; repaving projects on this thoroughfare have retained or reintroduced setts to give additional historic character to these neighborhoods. Part of this character includes the tracks of the 23 trolley, though the modern tracks are encased in concrete slabe rather than setts, and the trolley line itself is currently operated by buses.
In many cities (including Philadelphia, as exemplified above), setts have often been used for pavement around street-running trolley or tram lines, in the same manner as brickwork.
Belgian block is usually granite. The meditation hall of the Poison Ivy Ashram on the east side of Cayuga Lake (New York State) is paved with setts of granite.