Hagia Sophia in Istanbul, is an impressive old building and still in use. It was built in 537 CE as a Greek Orthodox basilica. In 1451 it was converted to a mosque and the mosaics of people were plastered over.
In 1922 the Ottoman Empire broke up and a year later Turkey was created with Ataturk the first president. He was a radical reformer, ruthless, and still revered today. He made sweeping reforms to the country, he abolished Sharia courts, gave women full political rights to vote and hold office, and changed the alphabet.
And made Hagia Sophia a museum.
Today things are swinging back the other way, under Recep Tayyip Erdogan, prime minister since 2003, other Greek churches have been converted to mosques. There is a battle to make Hagia Sophia a mosque and plaster over the original artwork, again.