Work on the Blue Mosque began in 1609 on the instructions of the 19-years-old sultan Ahmet.The architect of the masterpiece took seven years to complete. All the standard features of mosque design can be seen,but the Blue Mosque is unusual in having six minarets-one at each of the four corners, as might be expected, and another two, slightly shorter, at the outer edge of the courtyard. According to one story, the young sultan offended authorities at Mecca, the very heart of the IsIamic religion,and was required to pay for the construction of a seventh minaret for the mosque, ensuring that it would have no rivals.