Well, Chris Heard gives a good description of this set in his review below, and based on his review I bought this set. I was looking for something along the lines of a 'Caves Details meets the Temple series' and this is perfect.
What I would add though, is that the underground cave part fits perfectly with the Caves of Peril set. Especially important ( to me ) are the addition of these pieces especially the 'corner pieces' that neatly stop you having to add about 12 entrances into a Cave of Peril.
Overall a fantastic set, and I would say a total MUST buy if you have Caves of Peril, and vice versa, if you have this, then buy the Caves of Peril ! Brilliant !
[5 of 5 Stars!]