Istanbul, long regarded as the capital city of the Roman Empire and Europe’s most populous city, is slated to open an underwater hotel by 2010. Built underneath the city’s center, the 7 floor, seven star (I thought it went to 5) hotel will feature all ocean facing rooms, an exhibition hall and restaurants. If you’ve seen Jaws three then you’ll probably opt for the cultural experience, at least the sleeping part, above water. Fiji recently announced an underwater hotel aptly dubbed the Poseidon.
More info here.