Complex sentence: The first church at the site, "Santa Maria a Magnanapoli", was built sometime before the year 1000 and belonged to the same community of Dominican nuns who serves this church today from the Convent of San Sisto Vecchio at the Baths of Caracalla.
Split into simpler sentences: The first church at the site, "Santa Maria a Magnanapoli", was built sometime before the year 1000. It belonged to the Dominican nuns, who still serve this church, at the Convent of San Sisto Vecchio at the Baths of Caracalla.