Sound like the plot of "Poltergeist"? Yeah, except "Poltergeist" was pure imagination, and Cheesman Park's haunted history is true. Here's the Horror Channel's take on it:
Ownership of the cemetery passed ... to a cabinet-maker named John Walley, who was also an aspiring undertaker. He did not, however, seem to have a good head for business, and Denver City Cemetery fell into a state of disrepair. Most of those buried there were criminals, victims of smallpox, and transients; and general interest in upkeep on the place dwindled. Headstones were toppled, graves were often vandalized, and occasionally cows were allowed to graze among the graves. The City decided enough was enough.
Through some unknown means, someone in the U.S. Government dug up a document that reported the land was part of an Indian treaty and therefore was federal land. The Government then sold the cemetery to the City of Denver, all 320 acres of it, for two hundred dollars. The following summer the City Council announced that all concerned parties had ninety days to move their loved ones for burial elsewhere.
Because most of those buried in the cemetery were homeless or criminals, the majority of the bodies went unclaimed. In 1893 the City of Denver awarded a contract to an unscrupulous undertaker named E. F. McGovern to move the unclaimed bodies. McGovern was to place each exhumed body into a fresh box for delivery to a new burial ground, at which time he was to be paid $1.90 per box. The problem was, the new boxes were only three feet long and one foot wide, making many of the corpses far too large to fit. McGovern had a solution, however. Those that would not fit were hacked to pieces and shoveled into the boxes.
The looting and grave desecration caused the City of Denver to shut down the project, leaving hundreds of open and empty graves. Other graves hadn't been touched. Eventually the bodies were forgotten, leaving more than 2,000 graves under what would soon become Cheesman Park. The city simply built over the existing graves.
Today, residents of the neighborhoods around Cheesman report hauntings of various kinds, and if you're made of sterner stuff, you can even spend a night in one of several "haunted" B&Bs in the area ... boo.