Every now and again, you come across something beautifully designed, well-made, of pure quality (and yes quite expensive).
Two years ago, Emilia wanted a marble run for Christmas and I think I disappointed her at the time as I didn't get a zippy plastic one, or even one of those curved wooden ones. No. I found Cuboro on the web and fell in love. This is an example of a really good toy, though possibly a bit old for a four-year old. It is a set of wooden cubes, each with a different way for a marble to pass across, or through it and which can be built up into an endless set of variations of a marble run. We've just bought some more (from Manufactum) for this Christmas and now Emilia is old enough to build her own, we shall all be able to build bigger and better runs. I suspect there is a lot of educational value to be had for small people constructing different and intricate ways for a marble to run, but mostly it's a lot of fun, if you like that kind of thing. To show you what I mean, here's a video of our kitten, two years ago thoroughly enjoying himself.