Marble Castle

A castle whose tops are one continuous marble run. Drop a marble at the first tower and it rolls tower to tower to the ground — a river, or a roller coaster — with every hump and dip placed to steer its speed. Gravity does all the work. The battlemented tops are one channel carved through the towers, its floor shaped so the marble never stalls on a hump and never leaves the track in a dip, then one long descent out through the front wall. Two runs: a river with a hill every hand's breadth, or a coaster with fewer, deeper dips. Four, six or eight towers; takes an ordinary 16 mm marble. The name raised on the front wall. Made as one piece — nothing to assemble.