Cobblestone is a natural building material based on cobble-sized stones, and is used for pavement roads, streets, and buildings.
In England, it was commonplace since ancient times for flat stones with a flat narrow edge to be set on edge to provide an even paved surface. This was known as a 'pitched' surface and was common all over Britain, as it did not require rounded pebbles. Pitched surfaces predate the use of regularly-sized granite setts by more than a thousand years. Such pitched paving is quite distinct from that formed from rounded stones, although both forms are commonly referred to as 'cobbled' surfaces. Most surviving genuinely old 'cobbled' areas are in reality pitched surfaces. A cobbled area is known as a "causey", "cassay" or "cassie" in Scots (probably from causeway).
Setts are often idiomatically referred to as "cobbles", although a sett is distinct from a cobblestone by being quarried or shaped to a regular form, whereas cobblestone is generally of a naturally occurring form.