Although the Saudi authorities claim there is no evidence to confirm it, many Muslims believe this is the spot where the Prophet Muhammad was born in around AD 570. As a result this modest two-storey structure, which is now a library, is surrounded by signs warning against 'disapproved' devotional behaviour, but there's no information about the Prophet's birth. That hasn't stopped some pilgrims from inscribing their blessings and prayers on the walls.
The library is in the northwest, within the Holy Mosque's boundary.