The building pillowed by the three roman arches is Cuenca’s town hall, which also marks the entrance to the plaza.
The anime gets most of its exceptionally lavish backgrounds from the city’s well-preserved, historic town center, which is perched atop a steep hill in the north-eastern part of Cuenca.
The 14th century house nowadays hosts spanish abstract art galleries, so you can probably imagine that the inside looked quite different from the anime.