We took Isobel to see the Eiffel Tower today (not to go up it, mind: at her age the excitement is all about seeing it from the outside. The view from the top is so abstract there wouldn't be any point).

Anyway – she was rather more impressed than I hoped, and it was almost an effort to get her into the playground to run off a bit of steam.

When she'd finished sliding and rocking and climbing, we sat down for a few minutes by an old-fashioned carousel. But when we got closer we realised it was actually much more unusual than it looked.

For a start, it was operated by hand. Which meant the poor guy had to start it by pushing it off, and then had to crank with a big lever. And just before their ride started, each child was given a white stick about the size of a drumstick.

At first, this mystified me. But once the ride got underway, everything was clear. On the perimeter of the carousel there was a small board, with metal rings poking out of the bottom. As the children on their horses rode past, they were supposed to skewer a ring with their stick. If they did, another ring dropped down to take its place, and so the game went on. The winner was the kid with the most rings at the end of the go. It was a sort of jousting for toddlers.

Well, they loved it – and it was a treat to watch. The delight on the kids' faces as they played this game was a joy to behold – and I defy anyone not to have fun watching. The girl operating the jousting machine was a true pro. As well as being able to unjam the (ancient) machine in the split-second she had to do it before being stabbed by an over-jealous child, she made sure even the tiniest toddlers ended up getting at least one ring by helping them out. The smiles of these really small kids when they finally did what they'd been trying and failing to do for the whole ride were a treat.

I don't know how long that thing has been there – but I wouldn't bet against it being a hundred years old. And it's been delighting kids all that time. With no lights, no noises, no licensing, nothing. Bit of a treat, really – and I can't wait to take Isobel there for a go.