Visitors are allowed to go inside the submarine to see what the interior of a submarine from that era looks like. It certainly is no luxury vessel. The interior is really quite cramp with a narrow passage from the back to the front of the ship, and hatches that lead up into other areas that is closed to visitors.
There are torpedo bays with a lingering odour of diesel where torpedoes once sat in wait its turn to be launched at enemy vessels. There are various stations with all sorts of meters and switches; perhaps for communications, scanning the area around the submarine, and various controls. There are also sleeping quarters for the crew and a better room for the captain.