Ascending and Descending, Lego style, by Andrew Lipson
Oh yes, M.C. Escher, in the form of hundreds and thousands of plastic bricks. The ultimate in obsessive compulsive, nerdy goodness. Lipson provides detailed progress shots on his website, so you can figure out how the mind bending constructions actually work.
Montage via over the next and on the table.
Images, from top: Ascending & Descending, Relativity, Belvedere, Waterfall, Balcony