#1 Sheikh Zayed Grand Mosque (Abu Dhabi, United Arab Emirates)
The Sheikh Zayed Grand Mosque in Abu Dhabi is one of the world's largest, with room for 40,000 worshippers. Its design blends Moroccan, Moorish, and Indo-Islamic styles. Inside, see the world’s largest hand-woven carpet and Swarovski crystal chandeliers. Tours welcome non-Muslims, except Friday mornings. Note that a strict dress code is required for entry.