The Octacube is a large stainless steel sculpture displayed in the atrium of the mathematics building at Penn State. It represents the 24-cell, a four-dimensional geometric object that has no direct equivalent in three-dimensional space — the sculpture is essentially a three-dimensional shadow of something that cannot physically exist in our universe. At over 1.5 metres in diameter, it is a striking object even for visitors with no mathematical background, catching light beautifully and changing in appearance as you move around it.
The mathematics department building is open to the public and the sculpture is freely viewable during regular hours. It sits in good company — the building contains other mathematical art and visualisations throughout its corridors. The Octacube is the kind of find that justifies a detour: a genuine work of mathematical art, created in memory of a real person, free to see, and stranger and more beautiful than any description quite captures.