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.