<P> A perimeter block is a type of city block which is built up on all sides surrounding a central space that is semi-private . They may contain a mixture of uses, with commercial or retail functions on the ground floor . Perimeter blocks are a key component of many European cities and are an urban form that allows very high urban densities to be achieved without high - rise buildings . </P> <P> Other uses of the term "blocks". </P> <P> In North American English and Australian English, the word "block" is used as an informal unit of distance . For example, someone giving directions might say, "It's three blocks from here". </P> <P> In British English the term is very rarely used to express a measure of distance owing to blocks not being used in town or city planning in most countries . However it is often used to describe a short walk around the local area, as in "walk around the block". </P>

What does it mean to walk a block