Cool Tools reviews Cuboro, a set of somewhat expensive ($155 for the standard set), but awfully fun-looking wooden blocks that have holes and channels in them that let you build 3D marble paths
This is the best toy I have seen since Lego. I recently purchased a set for my 3 year old son, and we both have been having a blast with it ever since. The basic idea is simple: marbles and a track. The interesting thing is that the track is built out of individual wooden blocks with curves and channels cut into them, allowing you to create a track of whatever shape your imagination can conceive. The marbles are moved along strictly by gravity, falling from one level to another and cutting back and forth through hidden tunnels.
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