This was another project from last summer that was a huge hit. We did a Marble Run using paper towel rolls a few years ago and Cole loved it. This time I tried something a little more sturdy. I used PVC pipe, a few connectors and some suction cups.
I bought Suction Cups at Lowes and removed the hook part. Then I drilled holes in the pipes and in the connectors and shoved the end of the suction cup into the hole.