I got this idea from the book "child's play" Maja Pitamic. Its a lovely Montessori book full of ideas for play. I used some plasticine in different colours to make a curvy racetrack then chose some materials to create different sensory awareness in each colour. We found felt, soup mix seeds, shoelace, cut up sponge, matchsticks, marbles and rice.
The bumps and the bends made for some important language skills about smooth,rough,bumpy,rocky and zig zagging.