I remember in BG1 + 2 there were very few dungeon areas, they had mostly outdoor and city area combat areas, and there was only one massive dungeon to each as an expansion (maybe dungeons werent a popular theme back then?).
So far on top of the starter dungeon, Ive found the bit under Gilded Vale, Caed Nua, underneath Caed Nua, Lighthouse, Tower, Sewers and hopefully many many more yet to come!