 The number of tilemakers employed by the imperial workshops dwindled so that by 1566 only three remained.With the construction of the Süleymaniye Mosque, Iznik became a major center for the manufacture of underglaze tiles.Archaeological excavations in İznik conducted by Oktay Aslanapa in the early 1960s revealed that the town had been an important centre for the production of simple earthenware pottery well before the introduction of the blue-and-white fritware.