Seaananews Crowds have gathered in Istanbul as the Hagia Sophia opened for Friday prayers for the first time since Turkish authorities ruled it could be converted into a mosque . About 1,000 people were allowed in through security checkpoints , while others laid out prayer mats outside . Built 1,500 years ago , the Unesco World Heritage site was originally a cathedral , then became a mosque and most recently , a museum . Earlier this month a Turkish court annulled its status , saying any use other than as a mosque was " not possible legally " . Tap the link in our bio to read more about the building's history and why the change has been met with a mixed response.