The first reason as to why the Holy Prophet (Sallallahu alaihi wa sallam) was taken to Masjid Aqsa was that this should serve as a proof for the disbelievers. The heavenly worlds are not seen by the disbelievers, then how would they affirm and acknowledge Meraj? They had seen Masjid Aqsa. They asked the Holy Prophet (Sallallahu alaihi wa sallam) about Masjid Aqsa. The Holy Prophet (Sallallahu alaihi wa sallam) told them about Masjid Aqsa and about the caravans, which He (Sallallahu alaihi wa sallam) had seen on the way, so that with His true words, a proof is established for the disbelievers. (Subul Ul Huda War Rashad, Vol. 1, Pg. No. 17)