I found these "10 Incredible Underground Lakes & Rivers" through Digg.com
underground lake near Macan Che on the Yucatan Peninsula
underground lake in Messalini Caves (found when the roof of the cave collapsed after an eartquake in 1953)
Banff, Canada (love the waterfall)
Luray Caverns, Virginia (Shane and I pass the exit for these everytime we go home to Erie)
All of these amazing caverns reminded me of when we went on our honeymoon in Cancun, Mexico and went to a cenote. It was like paradise! Some lady even said that when she was swimming in it!
Where would your paradise be!? Let me know if you have been somewhere that has taken your breath away, because I want to travel and see as much as I can!