The Falkirk Wheel is the world's only rotating boat lift, and even if you have no particular interest in canals or engineering, it is worth the trip. The structure is a double-headed arm, each end holding a gondola filled with water — and, when it's working, canal boats. As the wheel turns, boats in the upper gondola descend while boats in the lower gondola rise, the balanced loads requiring only as much energy as boiling a kettle. The mathematics of it is almost offensively elegant.
The visitor centre at the base explains how the wheel works and the history of Scotland's canal network, which was built at enormous expense in the late 18th century to carry goods across the country and then largely abandoned when the railways arrived. You can take a boat trip on the wheel itself, riding up through the turn in one of the gondolas, which takes about 45 minutes in total. The surrounding canal basins are pleasant for a walk and the wider Helix park connects down to the Kelpies a couple of kilometres away.