This may be one of the coolest things I have seen in a long time. It’s like something out of a James Bond movie. This dome is covered in algae because it is underwater. The only way to access it is to enter a mansion. You must find a secret wooden door that leads you down some steps where you row a boat through an underground corridor before reaching two large doors that open into this enormous domed room under a lake. Did you get all of that?
In 1889 Whitacker Wright a British mining mogul who was very eccentric built this as a secret billiards room. It is over 125 years old but still in pretty good condition. All the light is natural, using a series of glass skylights to let sunlight down into the secret rooms.