That picturesque barn in the Swiss countryside might be a former Army bunker

Switzerland may not put a foreign invasion at the top of its list of threats. But, during the 20th century, Europe saw its share of devasting wars.

So Switzerland built thousands of bunkers and fortesses across the country. Most have been decommissioned; many have been put to commercial use. Entrepreneurs have used them to start hotels or data centers, museums and cheese factories.

The Swiss army has sold most of these former defenses, but Reuters reports that about a thousand unused bunkers remain, many still disguised as houses and barns.

Photographer Arnd Wiegmann has been visiting some of the military bunkers and fortresses across Switzerland. Here's a selection of our favorite images from Weigmann's travels.