Many of its buildings are impressive, but the city's architectural jewel is the recently refurbished Eureka Opera House. Built in the fall of 1880 on the smoldering site of the burned-down Odd Fellows' Hall, its grand opening was celebrated with a New Year's Eve gala masquerade ball. The Opera House now welcomes small conventions from around the state, performances by nationally recognized artists, even dinner theater, a cosmopolitan touch long unavailable in Eureka. The 1877 Jackson House next door has been restored to its original elegance, with nine Victorian bedrooms upstairs and a bar and gourmet restaurant back in service downstairs.

There are a number of underground tunnels under this small town that link the buildings together, some were built to transport beer from the breweries to the saloons while others were built so people could move about during harsh winter weather. (they are not open to the public and are in disrepair).