In 1982 I bought my kids a game called Marbleworks, a box full of coloured plastic pipes and half-pipes and a handful of marbles, which they played with for the next ten years. In 2008, I dragged Marbleworks out of the closet and introduced it to Nya, the first grandchild, and last night the two of us built and rebuilt the plastic structure for over two hours.
Nya started by building a three-foot-high column and running some marbles through and then she got me to feed the marbles in from the top while she tried to stop them before they got to the bottom so she could let them out one by one. Then we spent some time grabbing the marbles from their landing spot at the bottom and quickly feeding them back in at the top so that the sound of the marbles was continous and, in at least for a while, soothing.
After that Nya decided that she wanted the column to zigzag, so we rebuilt and ran the marbles some more. I talked her into creating two entry points so we could hold marble races but Nya was quickly bored by that so we went back to one entry point and all the marbles starting together at the top and racing down. I suggested they were children rushing out of the building at 3 pm and from there we went on to BC Hydro workers at the end of the workday and then ninjas being chased by their wives (of the ten marbles, half of them were "sparkly" so they were the girls), then monkeys escaping from the zoo and finally police officers (female) chasing bad guys.
When Nya was a few years younger I built a structure that ended in mid-air so the marbles fell straight down and bounced and rolled all over the floor. Nya loved our marble anarchy—she laughed and laughed and wouldn't stop playing until bedtime.
Marbleworks is still available from Discovery Toys.