Abu Dhabi is a city-state apart of the United Arab Emirates. Prior to 1971, Abu Dhabi was a country unto itself. Today, Abu Dhabi is among seven countries that were once independent but now fall within United Arab Emirates (UAE).
I have visited ancient mosques in Spain and have seen the Moorish castles of Portugal. Those sites are impressive and magnificent to behold. Today, one of the most magnificent mosques is located in Abu Dhabi, UAE — Sheikh Zayed Mosque.