The "Tower of Babylon" is one of the many puzzles that followed Rubik's cube. In principle it is a sliding puzzle. You must order 36 balls, so that there are 6 balls with the same colour in a column and ordered by shades. You can easily move them horizontally. They are fastened in a ring. Moving vertically is only possible with a trick: You can push a ball at the bottom to the middle (left arrow), so it disappears. Then the balls move down and form a gap at the top (right arrow). If you hold the tower horizontally, you can move the gap to another place. This is enough to solve the puzzle.