Tantallon Castle - Credit: Wikimedia Commons
Tantallon Castle is a ruined mid-14th-century fortress, located east of North Berwick, in East Lothian, Scotland. It sits atop a promontory opposite the Bass Rock, looking out onto the Firth of Forth. The last medieval curtain wall castle to be constructed in Scotland,Lindsay, The Castles of Scotland, p.440–442 Tantallon comprises a single wall blocking off the headland, with the other three sides naturally protected by sea cliffs. Read more on Wikipedia
Source: en.wikipedia.org