537: The Hagia Sophia is completed. One of the most beautiful churches ever built, Byzantine Emperor Justinian I had it built in Constantinople. It remained the world’s largest Christian place of worship until Seville Cathedral was finished in 1520, and it was converted to a Mosque by the Ottomans in 1453. In 1935, it was secularised by Ataturk and made into a museum.
1922: The first ever aircraft carrier is finished. The Japanese carrier, the Hosho, was launched from Yokohama, and the design would revolutionise naval warfare, permanently displacing the great battleships of the First World War in favour of quick airpower.