East Flanders and West Flanders are both located at the North Sea, in the coastal plain which is devoid of caves. There is also no mining, except for crude oil and gas. The only underground structures are subterranea, like cellar, but their numbers are also low. The most spectacular underground structures are the bunkers of the German Atlantikwall. However, West Flanders has none. The three sites are a historic casemate, a World War I bunker and a Cold War bunker.