I'm not actually sure if this is a bug or if there is some rule-based reason for it, but I am not being allowed to construct a crystal shrine on top of a water crystal. In the screenshot, the city directly next to the shard was conquered from an enemy. Neither this city, nor the one in the middle of the screenshot (Otar) is allowed to build the shrine. If this is not a bug, then might I suggest including some sort of message to the player telling them why they may not build a particular shrine? Right now it is sort of puzzling.

http://www.screencast.com/users/Cristofyr/folders/Jing/media/4b0c1508-40c3-4000-8418-808fdfc902d7

Edit: This happened also with a farm. There is fertile land next to this city that I should be able to farm, as I have the appropraite techology, but again the building is greyed out.

http://www.screencast.com/users/Cristofyr/folders/Jing/media/da571d53-b1df-4e81-89e3-4b57e2d2e85a