The sights at Old Sacramento State Park — about a mile from Great American Stamp Show — aren’t just above-ground.After several devastating floods they decided to raise the city by hauling in dirt. The project began in 1868 and finished in 1873.  This basically made the first floors of many buildings become the basements and the second floor became the first floor. Today, there are tours of Sacramento underground.There’s even an underground (or mostly underground) passageway back to the convention center area.