The Pontcysyllte is the world's longest and highest canal aqueduct

The Pontcysyllte Aqueduct carries canal boats across the River Dee near Llangollen in North Wales. At 336 yards long and 126 feet high, it is the longest and highest navigable canal aqueduct in the world.

I've been across it in a boat, and the lack of any barrier on the side opposite the towpath makes the whole experience feel like sailing across an infinity pool.

This Trekking Exploration video shows us the Aqueduct drained for maintenance. We see the bolts that hold the structure together and the plug that was once pulled to drain the canal into the Dee below.

If you want to see a child actor riding his bike off the aqueduct towpath and into the canal, see my first post on The Flower of Gloster.