Blue Room (Cave), Kauai
The Blue Room is documented in all the travel guides, but its really something off the beaten path. It's located at the end of the road on Kauai’s North Shore. I heard some other visitors comparing it to the Blue Grotto in Capri in Italy. Apparanetly, there is a daily show at the Grotto. The Blue Room is very quiet and serene, except for the bats.
This picture is of the cave entrance, there is no fee to enter but you need to be pretty fearless. The cave gets pretty shallow and dark as you get to the core. It has a sand floor and there are evidence of animals and other gross things around. We saw lots of bats flying around - (babies) but didn't want to stick around to see their momma.
Once you conquer that fear, you can enter the Blue Room. I don't know how but it is purely blue once you get in all the way. The clear water creates a fantastically electric blue world. Its amazing!
When we entered there were several people swimming, although it isn't allowed anymore, checked on the web. There is now a no-swimming sign.
I say if you have time, take a ride to the Blue Room. Just watch out for the bats and flagrants.
*Sorry no pictures of it, just the entrance to the cave!