Well, it's kind of a standard cardboard box, but with a few interesting features.

First of all, it's quite big for a cat, so she can sit and stand inside, but it's not too big to take a lot of space in my flat.

It is also very sturdy. A lot of cardboard boxes these days are very flimsy. The Fractal box is not flimsy at all and can take a beating from a cat.

It also has handle slots and cats love small holes to put their paws into.

Finally, it came with big foamed rubbery plastic inserts instead of regular styrofoam. Which are incredibly sturdy, impossible to break for a cat and they have big holes, so they serve as reconfigurable maze walls.