。
A famous architect built this house.
Literal
Famous-[attributive-な] architect [subject-が] this house [object-を] build-[past-た].
The new-information が marks 建築家 as the focus: 'it was a famous architect who built this house.' Where は would topicalize the architect as given information, が spotlights him as new. 建築家 ('architect') uses the ~家 suffix (いえ/か), which when read か means 'expert/specialist in X.' A quick example of focus marking.