I’m still toying with the idea of a Savage Worlds megadungeon. So I did a little research into the real world – always a useful place to start. My Google-fu turned up the following… if you know better, I’d like to hear it!
Tomb complexes do indeed exist; the pyramids, for example. They tend to be boring by dungeon standards, with a handful of chambers and (optionally) a maze of passages for intruders to get lost in.
There are underground cities, notably in Turkey – Derinkuyu is perhaps the most famous, at least eight levels deep and of unconfirmed extent horizontally. Living quarters, churches, a treasure chamber with a kick-ass spiral chute entrance, and rolling disk doors, all below the surface. It’s cool, but it’s not dungeon cool; no death-traps – people lived here, and small children and death-traps don’t mix. I’ve raised small children, and it’s hard enough stopping them from killing themselves while they explore normal environments. But I digress.
In more modern times, the threat of air attack has meant most fortifications have an underground component. Fantasy settings have airborne threats too – wizards, dragons, and so forth – so the dungeon might be a kind of castle, either abandoned or still in use. (I think it was Lew Pulsipher who first pointed this out to me in the 1970s.)
Again, reality is boring. People didn’t really build traps; they relied on guards, curses or taboos to keep intruders away, and had really harsh punishments for tomb robbers.
There are giant stone balls (as per Indiana Jones) in Costa Rica, but nobody knows when they were made, or why. Mostly they just sit there on the ground, alone or in neat patterns.
Not even the pyramids have traps, as far as I can tell. They do have pits (for drainage), falling stone blocks (to seal the passageways when the last workers left), and rooms full of sand (which is there to hide whatever is underneath, and make it harder to dig out; I’ve seen this trick still in use to protect archaeological sites in the Mediterranean).
Why no traps? I’m guessing, of course, but here’s my $0.02.
Firstly, economics; using D&D 3.5 as a source, I can hire half a dozen mercenaries (1st level warriors) for less than 500 gp a year, and have them guard a site 24×7; or I can spend anywhere between 400 gp and 241,000 gp on a trap. Guards are cheaper and more flexible most of the time.
Secondly, reliability; how long would a complex mechanism stay functional after you’d buried it? My guess is, not very long; there’s a particular house I go to most years, which lies fallow for six months before my visit, and the first thing I have to do each year is get the plumbing working again. So, I reckon you’d need a janitor going around keeping the traps clean and oiled, and at that point you may as well give him a spear and call him a guard.
Nope, none of these either, although there are numerous examples of ciphers. If you’ve built this complex to keep somebody out, why leave behind something that lets him bypass your security just by being clever?
I suppose one could have some analogue of the modern PIN pad or swipe card, but see comments about guards vs complex mechanisms above.
Dungeons in the RPG sense, as well as the traps and puzzles inside, have about as much evidence to support their existence as the monsters which supposedly infest them.
But that’s no fun, so we’ll continue to have them in our games, no doubt. That said, tombs are likely to be small complexes, or subcomplexes in larger delves; the bigger dungeons are probably cities or fortresses, or perhaps mines.