In the rainforests of central Mexico there is a tremendous pit of a cave, over 1000 feet deep. The cave is conical, wider at the bottom than at the top -- 160' x 205' at the top, opening up to a 440' x 995' chamber at the bottom. The surface at the top is uneven, the distance to the bottom is 1094' from the low side, and 1220' from the high point. Because of the birds who live in the cave, it's known as the Cave of Swallows.
As deep as the Cave of Swallows is, it's only the 2nd deepest in Mexico, and the 11th deepest in the world. The cave is deep enough, however, for a spectacular sport: BASE Jumping.
This is a video of some people base jumping the Cave of Swallows. Utterly insane, but thrilling.
Hat tip to Fogonazos.
No caves on Whidbey Island, sorry.