Imagine,

you are on the beach and bored,

if only you had taken some marbles with you, you could build a marble racetrack in the sand, like this one, I can not find out who made it but here are a few statistics about it, it is located at Klimduin School (near Alkmaar, the Netherlands) and runs for ±230 meter (±750 feet) with a height difference of ± 40 meter (±125 feet), the music is by Riding the Sunrise, it was quite entertaining, I almost spilt my coffee cheering one of the marbles on at one stage!