Based on a combination of area and capacity to accomodate worshippers, below is the ranking of the 6 largest mosques in the world:

1. Grand Mosque in Mecca

2. Prophet's Mosque in Medina

3. King Hassan II Mosque in Casablanca

4. Faisal Mosque in Islamabad

5. Badshahi Mosque in Lahore

6. Sheikh Zayed Mosque in Abu Dhabi