The Sacramento History Museum runs underground walking tours that descend below modern street level into the preserved first floors of Old Sacramento's historic buildings. When Sacramento raised its streets by up to 10 feet after the catastrophic 1862 floods, the original ground floors were buried and became basements — and in several cases they were simply sealed and left intact.
Tours descend into these preserved spaces, where original brick walls, wooden beams, and in some cases original signage and goods containers remain visible. The experience is genuinely eerie: you are standing in rooms that have been sealed since the 1860s, at what was once street level in the Gold Rush city. Tours run multiple times daily; book ahead in summer.