Kage no Sekai

Kage no Sekai is an amazing piece of interactive art.

Although at first glance it looks like a regular wooden table, if you look at the shadows on its surface you'll see the movement of mysterious life forms. When you approach it to have a better look, they sense your presence and hide away. They do not emerge while human shadows are cast over the table, but the life forms hiding within a distant shadow are watching them.