The tribe's buildings were actually villages in their own right, as later Spanish explorers must have realized since they called them by a name which is Spanish for town.
as は文の前半すべてを先行詞にしている（他動詞 realized の目的語がないので関係代名詞。疑似関係代名詞という言葉もある？）
越前敏弥『日本人なら必ず誤訳する英文』より。