The border wall between the U.S. and Mexico is not continuous. In some places there is a “triple fence,” in some places it’s a double fence and in some places it just stops. Border Patrol will tell you that the walls are not effective in stopping people from climbing over — the walls are only there to slow people down and give Border Patrol time to apprehend them.
Often, the terrain becomes so foreboding that a wall is impossible to build. In this example, the primary fence just stops and gives way to jagged mountains. The area is peaceful — no onslaught of people rushing through.