The Vekil-Harrach or Hadžijska mosque was built between 1541 and 1561 by Gazi Husrev-beg's quartermaster, Vekil-Harrach after whom it was originally named. It was used by pilgrims (hadžije) in the city before their joinery Mecca from here, it was named the Pilgrim's mosque.
It is fenced by a wall, inside which there is a stone fountain, which was renewed at the beginning of the 19th century by Sarajevo judge (kadija) Mustafa Fevzi, which is what the inscription is about.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.