One without a whole bunch of ramps, surprisingly. The interior has living spaces and working spaces, housing both a lab and a crazy wooden maze of banisters and staircases.
Kamen himself calls his house a "cross between a technology museum of old stuff and Willy Wonka's Chocolate Factory." Accurate only if Willy Wonka wore a jean suit. But, both are pretty admirable people, so it's a fair comparison.
Also cool are the sports facilities (tennis courts, basketball hoops, a friggin' softball field), plus a steam engine. All befitting an impressive man who was nevertheless able to put me to sleep at my own graduation. [WMUR - Thanks Eq!]