Al-Hayr was a massive hunting reserve to the east of Samarra. Surrounding it was a wall of coursed earth, enclosing an area of . The western portion of the wall bordering the central city was repeatedly demolished and rebuilt to make way for new construction, including that of the Great Mosque. Within al-Hayr were a series of racecourses, with each track measuring several kilometers in length. The layout of these racecourses varied; one was parachute-shaped, another bottle-shaped, and a third shaped as a cloverleaf.