We got this used and it may be ‘out of print’ now. It was an enormous hit with our two-year-old and remained so until he was 4 or 5. The tracks don’t fit with any of the other track-based toys we have, and some of the plastic fittings have gotten worn over the years, but we keep it in a plastic tub in the attic and pull it down every now and then for the kids to play with.
The tracks are patterned as road on one side and train rails on the other, so you can flip them depending on whether you want to drive a car or a train. Seems trivial as an adult, but it appeals to young kids.
And most of the fun is in putting it together, rather than actually playing with it. It’s essentially a 3D puzzle that the child assembles, with the trick being how to get the track to loop around and reconnect with itself.