So, Namaaz has been offered at Hagia Sophia and the Museum is now a Mosque.

The second Muslim Caliph, Omar bin Al-Khattab when visiting the Church of the Resurrection in Jerusalem (as Conqueror) was invited by the Bishop to pray inside the Church when it was time for prayers...

Caliph Omar refused to pray inside the Church or its courtyard and instead prayed outside on the steps next to the Church.

When asked by the Bishop why he prayed outside, the Caliph replied: “Muslims after me would have taken this Church as a mosque saying Omar prayed here"...

Later, the Mosque of Omar was built at the place where he had prayed. (Some sources have slightly different wordings, but in essence the above description is accurate of how events unfolded).

Erdogan is a bigoted opportunist and certainly not -as he would like to be- a Caliph.