St. Peter's Basilica, Vatican City — the largest church in the world, built over the tomb of the Apostle Peter on a site where Christians were executed in Nero's circus. Michelangelo designed the dome at age 71 and died before it was completed. Bernini designed the surrounding colonnade to embrace visitors like two outstretched arms.
© Bely Medved from Madison, USA, CC BY-SA 2.0, via Wikimedia Commons
