Additionally artificial lakes were constructed as part of Christian IV's large building project. These still exist to this day, and are simply referred to as the "lakes" (Skt. Jørgens Lake, Peblinge Lake, and Sortedams Lake). The area beyond the lakes, now heavily populated city districts, was then used primarily for grazing. It was prohibited to build beyond these original city limits so that the fortification’s cannons could have clear shot and so that the enemy could not find any hiding areas. The line that marked this "no build" zone was called the Demarcation Line ("Demarkationslinien") The line was moved further out as the shooting range of canons improved, and was not abolished until after the cholera epidemic of 1853.