We tried to estimate the mass of the boulder above it. We estimated 5 metres long by 5 metres high by perhaps 4 metres deep means 100 cubic metres. The density of andesite, a common volcanic rock in these parts, is about 2.5 tonnes per cubic metre. So the rock will have a mass of maybe 250 tonnes. And you sleep underneath it! It was hard to take photos inside but here is one of the cooking shelf. There was even a dust pan and brush in the bag. We signed the visitors' book but it is full so if you go consider taking an empty exercise book.
So where is it? It's a secret. No one on the Internet tells you exactly where but we worked it out. All I'll add is that it is at the very bottom of the crag. I climbed too far up at first.