MIHRAB محراب
A niche in the centre of a wall of a mosque which marks the direction of Makkah, and before which the Imam taken his position when he leads the congregation in prayer. In the Masjidu ‘n-Nabi, or Prophet’s mosque at at-Madinah, a large black stone, placed against the northern wall, facing Jerusalem directed the congregation, but it was removed to the southern side when the Qiblah was changed to Makkah.
The Mihrab, as it now exists, dates from the days of al-Walid (A.H. 90), and it seems probable that the Khalifah borrowed the idea

from the Hindus, such a niche being a peculiarly Hindu feature in sacred buildings.
The word occurs four times in the Qur’an, where it is used for a. chamber (Surahs iii. 32, 33; xix. 12; xxxviii. 20), and its plural maharib, once (Surah xxxiv. 12).

Based on Hughes, Dictionary of Islam