Complex sentence: It stands above the ruins of a pagan temple dedicated to Vesta, and was originally built as a circular building with twenty Corinthian columns, which is a common plan for a temple of Vesta.
Split into simpler sentences: It stands above the ruins of a pagan temple dedicated to Vesta. It was originally built as a circular building with twenty Corinthian columns, which is a common plan for a temple of Vesta.