1500 World population 400 million. 1501 First flush toilets. 1502 Coiled springs invented. 1503 Leonardo da Vinci begins painting the Mona Lisa. Michelangelo sculpts the David (finished in 1504). First handkerchief used in Europe. 1506 The building of St Peter’s Basilica started in Rome under Pope Julius II. The idea of a church for the [...]