Atlantic Wall Open Air Museum

The Atlantic Wall Open Air Museum is a military museum near Ostend in Belgium which preserves fortifications of the Atlantic Wall dating to the First and Second World Wars. The section of fortifications owned by the museum - over 60 bunkers and two miles of trenches - is among the best preserved sections of the defensive line in Europe. The fortifications survive because they were built on land belonging to Prince Charles, Count of Flanders who decided that they should not be destroyed after the war, but be kept as a national monument.

Source: Wikipedia