Welcome to day 4 of our countdown of the most frightening places in Chicago. Today we take a tour of The Murder Castle.

Chicago's 1893 Columbian Expedition World's Fair presented the world with a number of modern marvels: electricity, the Ferris wheel, Eadweard Muybridge's moving pictures, ragtime, the hamburger...and the nation's first high-profile serial killer, hotelier H. H. Holmes.

In 1889, Holmes (born Herman W. Mudgett) arrived in what is now Chicago's Englewood neighborhood and began working for Dr. and Mrs. Holden as a pharmacist. He seemed to be the perfect assistant and neighbor: able and industrious. His new acquaintances could not have imagined that this charming and dapper fellow had fled a succession of divorces and frauds—or that as a medical student he took out insurance on corpses, staged "accidents" with the bodies and collected payments upon the cleverly staged deaths.

When Mrs. Holden disappeared shortly after Dr. Holden's death of cancer, Holmes told the community that she had headed west and that he'd bought the drug store. The business continued to do well, and Holmes soon bought the lot across the street at 63rd and Wallace and announced that he would build a hotel for the upcoming fair. Holmes built a hefty, three-story building with 60 rooms. There were hidden passages and secret stairways, trap doors, chutes plunging to the basement, a staircase that opened to the alley below. More ominously, there were asphyxiation champers, a dissecting table and a crematory. Holmes's "guests" would check in but not check out: he tortured and killed at least 27 but possibly hundreds of innocents.

He lured them to their deaths not only by advertising lodging to the fair's tourists, but by offering jobs to small town and country girls who he warned must practice absolute secrecy and tell no one their employment plans, lest his competitors steal his clients. He imprisoned these lone strangers, tortured them, and killed them. His wife disappeared—he later confessed to killing her in a botched abortion attempt—but he already had a new consort, Minnie Williams, who became an accomplice in his villainous deeds. They committed a series of murders. One man they killed on a stretching rack Holmes had designed; Williams bludgeoned her own sister to death. Bizarrely, Williams acted as the witness when Holmes married another woman. The threesome lived and traveled together for a time, but Minnie—of course—disappeared. Holmes claimed she ran off to Europe; it seems more likely that Williams became another victim in Holmes's murder castle.

In 1894 Holmes killed his longtime partner Ben Pietzel rather than pay him his share of their latest take, and he added Pietzel's wife and three children to his entourage; he sent the woman east and told her he'd bring her children out later. He was arrested and briefly jailed for cheating in a horse trade. Then, he faked his own death and tried to collect the insurance money as someone else. When his insurance company balked, he just tried again. That scam worked—until an accomplice ratted on him. A Pinkerton agent pursued Holmes to Boston, and arrested him for another horse swindle. Meanwhile, the Pinkertons were starting to wonder where the Pietzel children were—and, following the trail through which Holmes forwarded his mail, they eventually found two of the children's corpses in Toronto. Finally, detectives got a warrant to search the Chicago Murder Castle.

The horrors they found there defy the imagination: a dissecting table, bottles of poisons, containers of quicklime and acid big enough to eat away a body, a gas chamber, coffins holding female corpses, an incinerator littered with charred human remains: the skeletons of small children.

Shortly thereafter—whether by arson as part of a cover-up or by disgusted neighbors, or an accident—the house burned to the ground. Neighbors avoided the block, claiming that the victims' ghosts haunted the building, their moans and cries lingering on. After Holmes was hanged for his crimes in 1895 following a swift trial, a number of the people involved with his trial died under bizarre circumstances, including a priest who had visited him before his execution, the doctor who certified him dead, the jury foreman, and others. This embroidered the legend: that Holmes was continuing his despicable behavior from beyond the grave, still killing for revenge and the joy of killing. In 1938 a US Post Office was erected at the site, but the rumors did not fade. Reports of poltergeists and apparitions continue to this day, and some claim that Holmes's ghost also visits the nearby Museum of Science and Industry, one of the few remaining structures from the 1893 Exposition.

Would you dare to get a room here for the night?