It's a very good experience for a stay at a bunker to understand the life in a bunker. Air conditioning at 14C, no windows, narrow corridor and basic continental breakfast are overall offering by the host.
A complementary visit to bunker is offered that more facilities are opened for visit to provide a better understanding of the life in a bunker.
Honestly, one night stay is fine and enough.
P.S. The host employs students and disabled people, it is a big merit.