A polyhedron constructed by ruling equally spaced vertical lines along the surface of a cylinder together with circles around the cylinder at equally spaced heights. Amazingly, joining neighboring points in triangles and letting gives a surface whose total surface area approaches, not that of the cylinder, but infinity.
Schwarz's Polyhedron
See also
CylinderExplore with Wolfram|Alpha
References
Ogilvy, C. S. Tomorrow's Math: Unsolved Problems for the Amateur, 2nd ed. New York: Oxford University Press, 1972.Wells, D. The Penguin Dictionary of Curious and Interesting Geometry. London: Penguin, pp. 224-225, 1991.Referenced on Wolfram|Alpha
Schwarz's PolyhedronCite this as:
Weisstein, Eric W. "Schwarz's Polyhedron." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SchwarzsPolyhedron.html