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Almost too well known to be included, the garage where Bill Hewlett and Dave Packard built their first product — an audio oscillator used by Disney — is now a listed building, to be an inspiration for generations of entrepreneurial engineers as yet unborn. Other famous garages include the one in Menlo Park where Sergey Brin and Larry Page started Google, and the Los Altos carport where Steves Wozniak and Jobs kicked off Apple.
Real-life visiting potential: 5/10. It's not nicknamed Shallow Alto for nothing.