He did appoint his royal architect Sedefhar Mehmet Ağa, a pupil and senior assistant of the famous architect Mimar Sinan to be in charge of the Mosque construction. The organization of the work was described in meticulous detail in eight volumes, now found in the library of the Topkapı Palace. The opening ceremonies were held in 1617 . The sultan could now pray in the royal box which called hünkâr mahfil. The building was not yet finished in this last year of his reign, as the last accounts were signed by his successor Mustafa I. Known as the Blue Mosque , Sultan Ahmed Mosque is currently one of the most impressive monuments in the world.