The Holbrooke Hotel on Mill Street is the oldest continuously operating hotel in California's Mother Lode, and it is still a working hotel. The Gold Rush-era building has been restored without being sanitized: the long wooden bar in the saloon downstairs is original, and the upper floors retain period character without the scrubbed lifelessness of many Victorian restorations.
Stop in for a drink at the saloon even if you are not staying. The bar is a genuine period piece, and the atmosphere — particularly on weekend evenings — captures something of what this town must have felt like when it was full of miners spending fresh gold. The hotel is well-maintained and a good base for exploring both Grass Valley and nearby Nevada City.