What now are comfortable patios outside bars and restaurants in Lower Downtown, once were part of an underground network of tunnels that allowed affluent folk to travel by horse and buggy from Denver Union Station to hotels and businesses in the blocks nearby. They’re an incognito part of Colorado’s heritage that is at risk of being lost. Denver’s downtown underground — along with subterranean places in other cities across the state including Grand Junction, Durango, Fort Collins, Pueblo, Salida, Florence, Cañon City and Trinidad — made Colorado Preservation Inc.’s 2018 Most Endangered Places list. Back in the 1880s, before the car was invented, the tunnels were used by the wealthy, allowing them to avoid grime and thievery when they arrived in Denver.