Switzerland's Centi Bunkers - Centurion Turrets in the Swiss Mountains -

When I was in Germany for a few days in 2009, The Chaplain of Landstuhl took me and other soldiers to the Saar to view part of the Nazi Germany Siegfried line. This was bordering France. There is at least one museum that has a Panther tank turret used as a stationary pillbox to defend the German border during World War 2.

Switzerland upgraded this concept during the cold war.