Ruins of Tombs

I've finally finished the game, well, so i thought, but have heard people talking about places like Ruins of Tombs as places they farm, and i've not come across these places. Obviously with nothing else to do, besides mess about in FoW, SF etc i want to visit these other places i seemed to have missed. Can any kind soul advise me where the Ruins are, and also what other places im likely to have missed out on!

My understanding is, from Dragon's Lair, head north through the exit, and then through the portal in the Tomb of the Primeval Kings.