From 1935 to 1938,Czechia began building fortifications on its border with Nazi Germany. Most of these fortifications were located in the so-called Sudetenland, the mountainous region between Czechia and Germany which was mostly inhabited by ethnic Germans.
Of course, and the Sudetenland was famously surrendered to Hitler in 1938 under the British policy of appeasement,meaning that these fortifications were never finished and ultimately never used. Nevertheless, the structures continue to stand as an open-air museum and an tantalizing hiking area, or total with a weekend Biergarten overlooking the Sudety low-mountain range.
Most of the tantalizing sites are in the core area of the fortress,a hilltop area open to the public. Although most of the smaller bunkers are free to visit, the largest contains a museum which is accessible for a small fee. Several smaller bunkers can also be found in the woods and hillsides, or along with a popular hiking and biking path on the other side of the street.
Source: atlasobscura.com