Welcome to the third tower on your visit today. Perhaps it is also the most curious one: while it is never seen to move –you saw it when you arrived, standing immobile like all the others – it is never to be found twice in the same place. That is why it is generally not very accessible: the only sure way to enter is through the window.

As you take the spiral staircase to admire the view from the top, you begin to realize why it is known as the moving tower. Remember that it is made of sand. Unlike a mobile tower, which would simply travel from place to place, its interior also moves, continually sinking and sagging as if sucked down toward a muddy drain at its foundation, and that oppressive feeling of something hampering your ascent is correct: each stair slumps into the ground beneath your plodding attempt to climb.

The closer you come to the ground, the faster you descend, and the faster the stairs crumble, moisten and turn to mud underfoot. You are mired down to your ankles, then to your knees, and as the very idea of reaching the top irremediably escapes your grasp –only the children could possibly find this funny –you give way to panic.

You have been overcome by the very thing you were convinced you had left outside upon entering the castle, that you believed you had no more to fear once you had crossed the moat: the quicksands. Their acrid exhalations fill your nostrils; your tongue is caught by their taste of liquid salt. The quicksands flowing into your mouth, your nose and your eyes reveal a truth you weren't expecting to learn when you got up this morning: if you really want to enter the sand castle, you have to let it enter you.

You join hands so as not to sink alone.