ara

Ara, arae, f., is first declension. The altar is the stone the sacrifice actually happens on, and it stood outside in the open; the temple behind it, aedes or templum, was the god house, not a place for a congregation. Roman religion did its business at the ara out front.

Fleeing ad aram was a claim to sanctuary, and that is the weight behind arae et foci, "altars and hearths", the standard phrase for everything worth fighting for. Ara Pacis and Ara Maxima are the famous ones. Late and ecclesiastical Latin generally prefers altare, altaris, n., for the Christian altar and leaves ara with a faintly pagan smell, so in a medieval text the choice of word is telling you something.