This pillar, the fifth one down from the ‘Aisha’ pillar and in line with Bab-e-Jibraeel is the approximate spot where the Prophet (ﷺ) led salah in Madinah when the Qiblah was towards Masjid al-Aqsa and at the opposite direction of Makkah.
References: History of Madinah Munawwarah – Dr. Muhammad Ilyas Abdul Ghani