Shelldock Isle - Lorwyn (LRW)

Hideaway (This land comes into play tapped. When it does, look at the top four cards of your library, remove one from the game face down, then put the rest on the bottom of your library.)
T: Add U to your mana pool.
U, T: You may play the removed card without paying its mana cost if a library has twenty or fewer cards in it.