All perfect praise be to Allah, The Lord of the Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
As a privilege granted by Almighty Allah, Al-Aqsa Mosque is one of the three mosques in which the reward of prayer is multiplied. This is supported by the Hadith where the Prophet (PBUH) said, "One prayer at al-Masjid Al-Haram is better than a hundred thousand prayers in any other mosque, a thousand prayers at my mosque and five hundred prayers at Al-Aqsa Mosque" {Related by Baihaqi in Shu`ab Al-Eeman}.
Al-Aqsa Mosque is the area surrounded by the rectangle-shaped wall in south east of Jerusalem or what`s known as "The old City of Jerusalem." Al-Aqsa is estimated at 144 dunums including the Dome of the Rock, the Masjid al-Quibli in addition to about two hundred other sites. The Dome of the Rock is the highest point at Al-Aqsa Mosque and is located in a central position centre.
In fact, Al-Aqsa Mosque refers to every site located within its walls. This includes all its yards, domes, the Dome of the Rock`s Mosque, Al-Buraq wall in addition to sites beneath the Mosque and above it. Judge Mojeer al-Deen al-Hanbali defined Al-Aqsa Mosque and outlined its various sites where he said: "Al-Aqsa Mosque is every site located within its walls." {Al-Ons Al-Jaleel Fi Tarikh Al-Quds wa Al-Khaleel}. Moreover, the Noble Quran named it Al-Aqsa Mosque(The Farthest Mosque) as reflected in the following verse, "Glory be to Him Who carried His servant by night from the Sacred Mosque to the Farthest Mosque; the environs of which We have blessed, that We might show him some of Our signs. Indeed He is the Hearing, the Seeing."{Al-Isra`, 1}.
In conclusion, the reward for praying at any spot within the boundaries of Al-Aqsa Mosque, at its yards and under its trees, is the same as praying inside the Mosque itself. And Allah knows best.