It's a canal lock.
It basically picks up the boat at the top and then rotates round while keeping the boat still and then docks at the bottom and the boat can continue on it's jaunt along the canals.
It's an impressive feat of engineering, Mr Lex might have some shots too as I believe he's from around those parts.
Sad truth is I live about a 20 min drive from there, in fact if I'm honest I'm at work at the mo and have to go and do an assessment for a training course and will be driving past the wheel on my way, shame I don't have the camera though