Remember those old fashioned wooden rollercoasters, the type you might see at the school fête?
The track has a double dip, the car only has room for two toddlers.
It’s pushed by hand to get it moving, goes in a straight line for 10m or so, before rolling back to the start.
Put one in a gallery, and dress the attendant as an old-style banker - pinstripes, bowler hat, brolly…
Free rides for all the visitors kids, possibly the last one they’ll ever get.