Many ancient ruins end up built upon leyline nodes, making menhir savant a natural fit.
Vanilla is thematically appropriate, as is world walker. For the latter, urban and underground are decent default terrains to take, but if you have some idea where the ruins in question are located, that can inform your terrain decisions.
If the ruins are all from the same civilization . . . maybe a reincarnated druid is a reincarnation of someone from said civilization? The GM might even work with it by providing flashes of ancestral memory from time to time (say, whenever your character dies). Not everybody is into a character whose primary power involves dying a lot, though.
A scholar- or "archaeologist"-type druid might even multiclass into Pathfinder savant for some interesting cross-class spells and abilities. (If you do, pick up psychic asylum as one of your esoteric spells. You'll thank me later.)