The 100 rooms of the H.H. Holmes house were filled with trapdoors, gas chambers, staircases to nowhere, and a human-sized stove.

If you were staying at the World’s Fair Hotel — more commonly known as the H.H. Holmes house, or “murder mansion” — you might run up a flight of stairs and find that it led to nowhere.

You’d open doors and see only solid brick. You’d enter a bedroom, hear hidden pipes quietly come alive, and smell the gas seeping in. You’d try to run and realize you were locked in. And even if the door opened, you probably couldn’t find your way out.

Only H.H. Holmes himself ever knew all of the castle’s secrets — including how many people died within its walls.

H.H. Holmes Arrives In Chicago

One of history’s most infamous serial killers, H.H. Holmes came to Chicago in 1886, leaving behind more than one previous life. Born Herman Webster Mudgett, previous scandals gave him good reason to change his name.

Like in college, when he worked in the anatomy lab and mutilated cadavers to defraud life insurance companies.

Or when he was the last person to have been seen with a missing little boy in New York.

Or when he worked as a pharmacist in Philadelphia and a young customer died after taking pills that he had provided.

Mudgett skipped town after all of these incidents and eventually became Henry Howard Holmes, who — soon after his arrival in the Windy City — got a job in a drugstore on 63rd Street, using his knowledge of medicine and his ability to charm everyone he met to secure his position.

Holmes was fashionable, bright, and likable; in fact, he was so charming that at one point in his life he was married to three unknowing women at once.

In 1887, he bought the empty lot across the street from the store where he worked and began construction on a three-story building, which he said would be used for apartments and shops.

The structure was ugly and large — containing more than 100 rooms and stretching for an entire block. Chicago was a city on the rise in the late 1880s and new construction was going up all over this stretch of the American Midwest.

The city was perfectly situated on the shore of Lake Michigan and it was the central hub for the expansive railroad networks that crisscrossed the nation, all extending like spokes in a wheel from the city of Chicago.

Chicago’s Murder Mansion

For his mansion, H.H. Holmes planned for the first floor to contain an entire block of storefronts he would be able to rent out to the flood of new businesses opening up in the city.

The third floor would contain apartments for the growing population of the city, looking to make it big in the Windy City–some of whom would become Holmes’s victims.

Those victims got to see the second floor–and the especially unlucky ones made it into the basement–which hid the elaborate horrors for which the H.H. Holmes house is now famous.

Holmes switched builders and architects frequently throughout the building’s construction, so no one involved was able to realize the gruesome end goal of all the odd parts.

The castle was completed in 1892 and by 1894 police would be exploring its winding passages while Holmes sat behind bars.

At first, they were confused at what they found.

There were hinged walls and false partitions. Some rooms had five doors and others had none. Secret, airless chambers hid underneath floorboards and iron plate-lined walls stifled all sound.

Holmes’ own apartment had a trapdoor in the bathroom, which opened to reveal a staircase, which led to a windowless cubicle. In the cubicle, there was a large chute that tunneled through to the basement. (Spoiler: It wasn’t used for dirty laundry.)

One notable room was lined with gas fixtures. Here, Holmes would seal his victims in, flip a switch in an adjacent room, and wait. Another chute was nearby.

All of the doors and some of the steps were connected to an intricate alarm system. Whenever someone stepped into the hall or headed downstairs, a buzzer sounded in Holmes’ bedroom.

Uncovering Chicago’s House Of Horrors

The first clue about the bizarre floor plan’s true purpose came to the cops in a pile of bones.

Most of them were animals, but some of them were human — so small they had to have belonged to a child, no more than six or seven years old.

When they descended into the cellar, the scope of the building’s hidden horrors was revealed.

Beside a blood-covered operating table, they found a woman’s blood-soaked clothes. Another surgical surface was nearby — along with a crematory, an array of medical tools, a bizarre torture device, and shelves of disintegrating acids.

Holmes fascination with dead bodies had lasted long past college, as had his surgical skills.

After dropping his victims down through the chutes, he would dissect them, clean them, and sell the organs or skeletons to medical institutions or on the black market.