Nearly all Holes were way up high. Well, the entrance point, anyway. The exit could be anywhere.
There's the famous one at the top of the steps of the Lincoln Memorial. It held the record for being the lowest recorded Hole until they found that freaky one at the bottom of that coal mine in the Central Atlantic Administrative Zone. They poured a block of concrete three meters thick around the one at the Memorial; it came out at three thousand meters over Manhattan and people were ducking into it with or without parachutes as the notion struck them. No one knows where the one in the coal mine comes out. No one that went in it has ever been seen again.
The Rabbit Hole is a science fiction novel of 81,000 words.