The Hagia Sophia in Istanbul also influenced Islamic architecture. When the Ottomans captured the city from the Byzantines, they converted the basilica to a mosque (a museum from 1934 until reclassified as a mosque in 2020) and incorporated Byzantine architectural elements into their own work (e.g., domes). The Hagia Sophia also served as a model for many Ottoman mosques such as the Shehzade Mosque, the Suleiman Mosque, and the Rüstem Pasha Mosque. Domes are a major structural feature of Islamic architecture. The dome first appeared in Islamic architecture in 691 with the construction of the Dome of the Rock, a near replica of the existing Church of the Holy Sepulchre and other Christian domed basilicas situated nearby. Domes remain in use, being a significant feature of many mosques and of the Taj Mahal in the 17th century. The distinctive pointed domes of Islamic architecture have remained a distinguishing feature of mosques into the 21st century. Influenced by Byzantine and Persian architecture, the pointed arch as an architectonic principle was first clearly established in Islamic architecture; as an architectonic principle, the pointed arch was entirely alien to the pre-Islamic world. Especially in the Persianate world, the slightly "depressed" four-centred arch or "Persian arch", has been the most common style used.