Italy: Layers Upon Layers
Down the block from the Pantheon is the church of Santa Maria Sopra Minerva, so-called because Rome's only Gothic church was built above a temple to the Roman goddess. Out in front is an Egyptian obelisk, mounted on the back of an elephant (!) sculpted by Bernini; inside Michelangelo, Fra Angelico, Filippino Lippi. The body of of St. Catherine of Siena lies beneath the altar (her head stayed behind in her home town).
Bonus: as we admired the elephant/obelisk, a Roman lady strolled by with a cute little Newfoundland bitch. (Yeah, I'm using little as a relative term here.)
Recycle, Recycle, Recycle
Rome's Basilica of Santa Maria degli Angeli was built on the ruins of the Baths of Diocletian.