This is the Büyük Mecidiye Camii (commonly known as the Ortaköy Mosque) which sits on the waterfront close to the Bosphorus Bridge (Boğaziçi Köprüsü). This neo-Baroque mosque was completed in 1856, built on the orders of reformist Sultan Abdülmecid, who contributed calligraphy to the mosque’s interior.
Here are details of the exterior and the interior (at the base of the dome).