Netherlands: Schokland
Schokland is a UNESCO World Heritage site and former island in the Dutch Zuiderzee, it was just a small elongated strip of peat land surrounded by seas. There was a small settlement here since the middle ages, constantly threatened by the rising seas. Finally, the flood in 1925 completely destroyed everything. Fastforward to 1942, and the entire area around was reclaimed from the sea and Schokland is now deeply inland.