Chalk hills extend across the county of Kent, from Dover to Gravesend, but most of the surface chalk is of a soft and porous quality, unsuitable for unprotected external work. The first example below shows how the medieval city walls, constructed in the 1380s, relied on a hard flint surface (much of which is now lost) to protect the internal blocks of chalk. The second provides a rare example of internal medieval walls showing a jumbled mix of chalk, flint and other stones.

Local examples (click to enlarge)