Another refurbishment of the mosque was carried out in 1571, when Ottoman emperor Selim II authorized court architect Sinan to enhance the structure. Sinan's flat roof was replaced with small domes. The Ottoman extensions are the earliest portions of the current edifice still standing. They include a small chapel on the north side and an infirmary on the east. The Great Mosque of Mecca is one of the holiest sites in Islam. It is also known as the House of Allah because it contains many features designed to reflect God's greatness, including the largest single-span wooden ceiling in the world. The original mosque was built in the 8th century by Abd al-Muttalib, father of Muhammad. Over the years, several additions were made to it, most notably by Sultan Abdulmumin in 1571. These renovations were done using only hand tools and no electricity! The current appearance of the mosque dates back to 1912, when it was restored by American architect William Newton Craddock. You may have heard that there are similarities between Islamic architecture and Gothic architecture. This is true, but they were developed independently of each other. Although Mecca has been known as "the city of three religions" since its founding by Abraham, Jews and Christians alike have been excluded from building churches in the city. However, this situation changed in 2015 when Chinese investors purchased the site where Mecca's old Jewish quarter once stood.