I dunno about Ultima III, but QotA had 'battle screen' sections of dungeon, which basically means a top-down section. I believe the altars are in such sections? I do know there's a three-way split in the Stygian Abyss, because I accidentally went around in a circle last time I played.
QotA is really awesome, I should play it again some time.
It had both top-down 'combat rooms' and a 3D first-person view (as did Ultima III.)
Of course, in Ultima III, you couldn't leave the top-down combat arena until the monsters were dead or you were. That was also fixed in Ultima IV, where you could chicken out at the cost of some Valor.
QotA is really awesome, I should play it again some time.