City block

In a city with a grid system, the block is the smallest group of buildings that is surrounded by streets.

City blocks may be subdivided into any number of smaller land lots usually in private ownership, though in some cases, it may be other forms of tenure.

City blocks are usually built-up to varying degrees and thus form the physical containers, or "streetwalls," of public spaces.

Most cities are composed of a greater or lesser variety of sizes and shapes of an urban block.

[1] This historic arrangement reflects organic development of structures and land usage, adapted to urban planning.

Exceptions include cities that were founded as Roman military settlements, often preserving the original grid layout around two main orthogonal axes (such as Turin, Italy); and cities heavily damaged during World War II (like Frankfurt).

Chen defines the supergrid and superblock urban morphology in that context as follows:"The Supergrid is a large-scale net of wide roads that defines a series of cells or Superblocks, each containing a network of narrower streets.

Diagram of an example of a rectangular city block as seen from above, surrounded by streets. The block is divided into lots which were numbered by the developer as shown in red here and as shown in plats . The addresses on this example 800 block are shown in black and the adjacent blocks are the 700 and 900 blocks. An alley shown in light gray runs lengthwise down the middle of the block. Streets are shown in dark gray. Sidewalks are shown in light gray. Avenues are shown in green with walkways shown in light gray from every lot to the street.
Chicago in 1857. Blocks of 80, 40, and 10 acres establish a street grid at the outskirts which continues into the more finely divided downtown area.
Same diagram of first illustration (see introduction), enhancing the "blocks without sidewalks", enfolded by the tiny green line. They are, with the inner alley and the sidewalks, sub-structures of the city block .
Interior of the Kone & Silta perimeter block, Helsinki , 2019