The U.S. Patent Hierarchy.

Taxonomy visualization of patent data / by Katy Borner ... [et al.], Bloomington, Indiana, and New York, 2006
Full color exhibition maps, charts and diagrams. Title from missing accompanying flier "A science exhibit that demonstrates the power of maps to navigate and manage physical places and abstract topic places." Published also in 1 videodisc. Complete set includes 22 maps.
See Places & Spaces, Mapping Science for publications related to these maps: http://scimaps.org/