Stone-built castles, mostly the defended residences of medieval lords, are amongst the best-known and most prominent of all ancient monuments and many, such as the Tower of London and Dover Castle, are major tourist attractions. A brief chronology and history of research are included along with descriptions of the asset type and its associations. The first stone castles were built in the 11th century, soon after the Norman Conquest (1066), and they continued to be built, re-built and extended over the following centuries. In that time castle design evolved (as described below) in response to military developments, architectural fashion, influences from abroad and changing social attitudes; this can be read in the fabric of surviving castles, even relatively poorly preserved ones. Castles are a major store of information about the changing ideas of the medieval centuries.