The main entrance to the ancient city, the Siq is a 1.2km-long narrow defile. Access to it was once spanned by an arch; its vestiges can be seen on either side of the pathway. A canal hewn into the rock runs along it; this channelled water from a spring into the city. High walls enclosing the defile rise to over 100m. The passage widens and then narrows several times, before suddenly revealing the pink façade of a temple-like monument, the Treasury, marking the entrance to the great necropolis.