Great Mosque of Córdoba begun

Near the end of his long reign, ʿAbd al-Raḥmān al-Dākhil — the Umayyad prince who had crossed to al-Andalus as a refugee from the ʿAbbāsid revolution and built an emirate — founded the great congregational mosque of Córdoba on the site he purchased from the city's Christians.

Its double-tiered horseshoe arcades in alternating stone and brick, multiplied by every enlarging emir and caliph after him until the forest reached some six hundred columns, became the architectural signature of the Muslim West. Even converted to a cathedral after 633 AH/1236 CE, the building is still la Mezquita.

The founding is dated by year — 169 or 170 AH — with no month carried; year precision, honestly.