According to string theory, spacetime as we know it isn't 4-dimensional, but 10-dimensional.  The next question is, where are the extra 6 dimensions that we don't see?  One answer is that they're 'compactified': roughly speaking, rolled up into such a small shape that they're unobservable by humans.

Calabi-Yau spaces may be that submicroscopic shape.  There are many such spaces, but being 6-dimensional, they're not easy to draw!  This model is a 3D cross-section through a likely space.  Surprisingly it's beautiful – a wildly self-intersecting ride.

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Calabi-Yau Manifold, 80mm glass cube – $72

Without illumination the crystal works best on a dark background.  It comes with clear rubber feet to avoid scratching your desk or mantel. On the left, this base lights up your manifold!  With a gloss black finish and white LEDs that are cool and energy-efficient, it's bright enough for the office by day, or a brilliant nightlight. Light base, 3½ x 3½ x 1" – $20