The Pontcysyllte Aquaduct in North Wales is the highest navigable aqueduct in the world. built in 1805, the ‘waterway in the sky’ enables the llangollen canal to travel over the river Dee valley 126ft above ground. It was designed by Thomas Telford and immediately hailed as an ‘engineering marvel’ by many.

As if the height wasn’t scary enough, only the side walkable by pedestrians is guarded by a rail.

One false move and you could very easily plummet 126ft to the ground…

sources: 1, 2, 3, 4