Pionen is an underground data center that belongs to the biggest Swedish internet service provider Bahnhof. It is located 30 meters under the granite rocks. It was built in a former bomb shelter, thus it can withstand a direct attack with a hydrogen bomb. Two Maybach MTU diesel engines from a submarine are responsible for backup power supply. Together they produce 1.5 megawatts of power. The entrance doors are 40 cm thick. The place is surrounded with the granite and it just mesmerizes with its beauty.