Hammersley Sofa

The moving sofa problem was formulated by the Austrian-Canadian mathematician Leo Moser in 1966. The problem is a two-dimensional idealisation of real-life furniture moving problems, and asks for the rigid two-dimensional shape of largest area A that can be maneuvered through an L-shaped planar region with legs of unit width.

https://en.wikipedia.org/wiki/Moving_sofa_problem

The sofa fits exactly in the corner - you may scale it down a little. The sofa on the GIF was printed at 98,5% size and was a little to small, 99 or 99,5 % should wort just fine. (Printed on Makerbot 2x)