A city block is the smallest street-wrapped building parcel
In urban design, a block is the tightest cluster of buildings ringed by streets—the fabric’s basic cell. Informally, “a block” also means the walk between two grid streets. Manhattan’s standard oblong runs about 264 by 900 feet; Chicago’s differ again.
Planned New World cities favor square or rectangular grids and often build perimeter blocks with street-facing structures around an inner court. Organic Old World cores rarely show neat rectangles, though Roman castra such as Turin preserve orthogonal axes, and some postwar rebuilds imposed new grids.
Philadelphia inspired New York’s later grid. Variants include superblocks bounded by arterials with only local lanes inside, plus subblocks and classic perimeter schemes. New York's version came with the Commissioners' Plan of 1811, and wartime destruction gave cities such as Frankfurt a fresh start.
Measurements differ from place to place. A typical Chicago block is 330 by 660 feet, so eight blocks one way or sixteen the other make a mile, a spacing other American cities copied, and central Melbourne uses the same dimensions after its original square blocks were split by narrow lanes. Across much of the United States and Canada each block of a street gets 100 address numbers. Blocks are usually divided into smaller lots, mostly privately owned, and the buildings along their edges act as the walls that frame public streets.
In Japan and China large blocks often hold an internal grid of narrower streets inside a net of wide roads, a pattern described as a supergrid. Barcelona retrofitted the idea onto its existing grid: each superilla groups nine blocks, bans through traffic, and caps speeds on the inner streets at 10 to 20 kilometres per hour.
Source: City block
