At 32.2,-51.5,-850.6 I found at least five dungeons, all huge with at least 6 or 7 rooms each, and lots of stairs. You will have to turn on noclip to get to them. I have lit up some of them with torches, but there are too many of them to light up them all in ten minutes. Download the map at https://www.dropbox.com/s/1bhlt7g4cj4jmq7/Dungeon.zip?m
The seed is 7846472670670620137