Could be both.

I was thinking that it would be the ruins of ancient, primarily stone structures that have aged poorly and been half-overgrown by the surrounding jungle, so creeping vines and the like. As for tombs, I imagine that there would likely be a vast number of underground ruins, possibly even the remains of some magic-powered parallel of a metro system. An entire undercity, just as dilapidated as the ruins above.

I'm certainly digging the feel of a jungle type of climate though. Possibly it could be a port city, as well? Just situated on the coast of some freshly-rediscovered (past hundred, perhaps two hundred years) jungle continent. That way you'd wind up with characters from civilized lands, locals who grew up in the ruins, orphans, local urban legends, etc.