$33M Custom-Built Mansion in Portola Valley, CA, Is a 'Livable Work of Art' $33M Custom-Built Mansion in Portola Valley, CA, Is a 'Livable Work of Art' A home in Portola Valley, CA, has landed on the market. The "livable work of art" took five years to build in one of the wealthiest communities in the U.S. Claudine Zap, provided by FacebookTwitterEmail Located in Silicon Valley, the “livable work of art” took five years to build in one of the country’s wealthiest communities. The custom-built mansion was designed to show off the owner's eccentric style, as well as her quirky decor and art collection.