I am fascinated by this "ballroom" under the lake. It was originally designed as a billiard room by the original owner. I've found several articles and some in depth Flicker photos of this place.
You can see the weeds and algae, after years of neglect, are covering up the windows.
The statue sits on the top of the dome, and when the room is lit up, it creates a great effect on the lake.
Just beyond the statue and room is an island that has glass skylights in the ground to illuminate the room below the island.
I would love to go check this place out someday! It's called Witley Park in England.
Check out these links for more pictures and articles on the place.
And my fave of 66 pics The Witley Wonder