regia

Substantive noun from rēgius (“regal, royal; a royal [thing]”) directly and via various ellipses of collocative terms with feminine nouns (e.g. domus, "house", and urbs, "city"). Compare the origin of Greek βασιλική (vasilikí, “basilica”), from the Byzantine Greek term βασιλική στοά (basilikḗ stoá, “royal building”).