Either intentionally or unintentionally. Include location and sculptor, if known.

Jane and John Kostick make many mathematically inspired sculptures some of which can be seen here: http://www.jjkostick.com/jjkostick/Welcome.html For example, Jane made a coffee table whose base is a trefoil knot. For two more examples of sculptures that Jane built, please see the December 2008 issue of the Girls' Angle Bulletin, which can be downloaded from: http://www.girlsangle.org/page/bulletin.html 


Perhaps these are too small to count as sculptures, but there is quite a respectable collection of models of mathematical objects on display in the Mathematical Institute in Goettingen. 


The french sculptor Bernar (sic) Venet: see http://images.math.cnrs.fr/BernarVenetdelartetdes.html 


The Found Math galleries at the MAA website include many mathematical sculptures. 





George Green's windmill in Nottingham has a sculpture with a mill wheel with Green's Theorem carved into it. 

