style of medieval fortification
A shell keep is a type of fortification in the medieval era. Shell keeps are stone structures circling around a raised area of the ground, called a motte.
The shell keep of Windsor Castle was built by Henry II and remodelled in the 19th century.
Restormel Castle built around the motte
Tamworth Castle, Staffordshire
Totnes Castle, Devon
Wiston Castle, Pembrokeshire