Because of its historical significance.!!
Mount Rushmore is not a World Heritage site. It has not as of yet, been nominated for status as a World Heritage site. The USA currently has 12 properties on the tentative list of World heritage sites.
Covering an area of 5,000 square meters the mosque has the capacity to accommodate 300,000 worshippers, therefore, capicity-wise it is the largest mosque in the world.
They are nominated by various countries based on their cultural and natural value, at which point a committe reviews their significance and opts whether to adopt one or not.
Some people consider the mosques Mali made as beautiful, as evidenced by the fact that the Great Mosque of Djenne was designated a World Heritage Site by UNESCO in 1988.
Some of the most elaborate mosques in the world are the Azadi Mosque, the Ruhy Mosque, and the Al-Saleh Mosque.
the biggest and the largest mosque in the world is MASJID-UL-HARAM it means KAABA-TULL AH
A natural or man-made site, area, or structure recognized as being of outstanding international importance and therefore as deserving special protection. Sites are nominated to and designated by the World Heritage Convention (an organization of UNESCO).
Taj Mahal The Taj Mahal is not a Mosque, it is a Mausoleum built in memory of Mumtaz Mahal. For the most beautiful mosque, Istanbul has the Blue Mosque and the Sultan Suleyman Mosque. Try the Faisal Mosque in Islamabad. Or Medina, the town of the Prophet Mohamed. There could be something like 40 around the world for which this description may apply
Al-Masjid al-Ḥarām ("The Sacred Mosque"), in Mecca, Saudi Arabia is the largest mosque in the world. The second largest mosque in the world is the Prophet's Mosque also found in Saudi Arabia in Medina, and the third largest mosque in the world is Goharshad mosque which is in the city of Mashhad, Iran. http://en.wikipedia.org/wiki/List_of_largest_Mosques
Updated AnswerAl-Masjid al-Ḥarām (المسجد الحرام) or "The Sacred Mosque") or the "Grand Mosque", is the largest mosque in the world.This mosque is Located in the city of Mecca (or Makkah) in the Kingdom of Saudi Arabia. It surrounds the Kaaba, the place which Muslims turn towards while offering daily prayers and is considered by Muslims as the holiest place on earth.The mosque can accommodate up to 4 million worshippers during the pilgrimage (or Hajj) period, the largest annual people gathering in the world.It is worthy to mention that The Faisal Mosque in Islamabad is the largest mosque in Pakistan and South Asia and the sixth largest mosque in the world. It was the largest mosque in the world from 1986 to 1993. Faisal Mosque has the third largest capacity of accommodating worshippers in its adjoining grounds after the Masjid al-Haram (Grand Mosque) of Mecca, the Al-Masjid al-Nabawi (Prophet's Mosque) in Medina.
Qubaa, in Arabia.