*Bat country*. Image designed by Gwen Fisher, engineered by Paul Brown. © Gwen Fisher.

These lucky people are climbing around a 22 feet (6.7 metres) tall structure composed of 384 softball bats, 130 soft balls and a couple of thousand pounds of steel. The structure represents a *Sierpinski tetrahedron*: a *fractal* which has finite volume but infinite area. The image only shows an approximation of the fractal of course, as it would be impossible to make a full-on Sierpinski tetrahedon with its infinite intricacy, but it's beautiful anyway!

The picture, designed by Gwen Fisher and engineered by Paul Brown, is one of the images that appears in the book 50 visions of mathematics, which celebrates the 50th anniversary of the Institute of Mathematics and its Applications.

You can find out more about fractals here.