The mosque was unearthed in Yamama district in al-Kharj governorate in central Saudi Arabia, according to al-Sharq al-Awsat.
The 18-strong team of archeologists was excavating ancient ruins belonging to the Stone Age in the area when the remains of the mosque was discovered.
Experts say the mosque was built in a period estimated to between the first and fifth Hijri centuries in the Islamic calendar (7th to 12th centuries C.E.).
It has two Mihrabs (Mihrab is a niche in the wall of a mosque, at the point nearest to Mecca, towards which the Muslim congregation faces to pray) and large round columns some of which measures 2 meters in diameter.
The mosque seems to have been the largest in Saudi Arabia after Al-Masjid an-Nabawi in Medina and Masjid al-Haram in Mecca at the time.