Lets start from 5 Largest Mosques in the World by Area and Capacity to accommodate worshipers.
Masjid al-Haram, Mecca, Saudi Arabia
Al-Masjid al-Haram, is the largest mosque in the world. Located in the city of Mecca, it surrounds the Kaaba, the place which Muslims turn towards while offering daily prayers and is considered the holiest place on Earth by Muslims. The mosque is also known as the Grand Mosque.
The current structure covers an area of 400,800 square metres (99.0 acres) including the outdoor and indoor praying spaces and can accommodate up to 4 million worshippers during the Hajj period, one of the largest annual gatherings of people in the world.
Al-Masjid al-Nabawi, Madina, Saudi Arabia
Al-Masjid al-Nabawi “Mosque of the Prophet”, often called the Prophet’s Mosque, is a mosque situated in the city of Medina. As the final resting place of the Islamic Prophet Muhammad, it is considered the second holiest site in Islam by both Shia and Sunni Muslims (the first being the Masjid al-Haram in Mecca) and is the second largest mosque in the world.
One of the most notable features of the site is the Green Dome over the center of the mosque, where the tomb of Muhammad is located. It is not exactly known when the green dome was constructed but manuscripts dating to the early 12th century describe the dome. It is known as the Dome of the Prophet or the Green Dome.
Imam Reza shrine, Iran
Imam Reza shrine in Mashhad, Iran is a complex which contains the mausoleum of Imām Ridhā, the eighth Imām of Twelver Shi’ites. Also contained within the complex include: the Goharshad Mosque, a museum, a library, four seminaries, a cemetery, the Razavi University of Islamic Sciences, a dining hall for pilgrims, vast prayer halls, and other buildings.
This complex is the center of tourism in Iran, visited by 15 to 20 million pilgrims every year. The shrine itself covers an area of 267,079m2 while the seven courtyards which surround it cover an area of 331,578m2 – totaling 598,657 m2 (6,443,890 sq ft).
Masjid Istiqlal, Jakarta, Indonesia
Istiqlal Mosque, or Masjid Istiqlal, (Independence Mosque) in Jakarta, Indonesia is the largest mosque in Southeast Asia. This national mosque of Indonesia was build to commemorate Indonesian independence, as nation’s gratitude for God’s blessings; the independence of Indonesia. Therefore the national mosque of Indonesia was named “Istiqlal”, an arabic word for “Independence”.
Hassan II Mosque, Casablanca, Morocco
The Hassan II Mosque , located in Casablanca is the largest mosque in Morocco and the third largest mosque in the world after the Masjid al-Haram (Grand Mosque) of Mecca and the Al-Masjid al-Nabawi (Prophet’s Mosque) in Medina. Designed by the French architect Michel Pinseau and built by Bouygues. It stands on a promontory looking out to the Atlantic, which can be seen through a gigantic glass floor with room for 25,000 worshipers. A further 80,000 can be accommodated in the mosque’s adjoining grounds. Its minaret is the world’s tallest at 210 m (689 ft).