Watch | Chicago Mysteries with Geoffrey Baer

Did a UFO fly over O’Hare Airport? How did the alligator later named “Chance the Snapper” suddenly appear in Chicago’s Humboldt Lagoon? Is Hull House haunted? Why don’t Chicagoans put ketchup on their hot dogs? WTTW award-winning host/writer/producer Geoffrey Baer sets out to solve these and other puzzlers in CHICAGO MYSTERIES. Audio-narrated descriptions of key visual elements are available.

Chicago made national headlines when an alligator, fondly nicknamed Chance the Snapper, showed up one day in the Humboldt Park lagoon. Geoffrey Baer explores this ongoing Chicago mystery.

Jane Addams’s groundbreaking settlement house was rumored to have ghosts and a so-called “devil baby.” Geoffrey Baer visits Hull House to hear those stories.

The “Sausage King” of Chicago once used the vats in his factory for an unsavory crime. Geoffrey Baer tells the story of the murder and visits the basement where it supposedly took place.

Putting ketchup on a hot dog in Chicago is, at best, quietly frowned upon, and at worst, likely to earn you the starring role as the butt of a joke. Geoffrey Baer explores why ketchup is forbidden with the help of Monica Eng.

On a frigid November day in 1915, a diver named William “Frenchy” Deneau was laying cable along the bottom of the Chicago River when he reportedly found a mysterious 40-foot-long vessel. What was the vessel, and how did it get there? Geoffrey Baer gets to the bottom of these questions.

The northwest suburb of Niles has its own replica of the Leaning Tower of Pisa, the famously askew belltower in Italy. Geoffrey Baer and Jessica Mlinaric investigate.

While the word monument may evoke images of grand structures visited by bustling crowds, Chicago’s oldest monument is a bit more subtle than that – and a lot more remote.

Why is the world’s first nuclear reactor buried in a Cook County forest preserve? Geoffrey Baer investigates with the help of Jessica Mlinaric.

In Chicago's Chatham neighborhood, there is a stretch of small homes with unusually large front yards. They're called "garlows" – a combination of "garage" and "bungalow."

Indigenous nations such as Ojibwe, Odawa, Potawatomi, Miami, and others – as well as their roads – were here long before Chicago was incorporated.

Who authored an encyclopedia manuscript on Chicago mobsters? Geoffrey Baer speaks with the man who discovered and later published the amazing artifact in a resale shop.

Does a University of Chicago sculpture cast a shadow of a hammer and sickle? Geoffrey Baer speaks with the artist to get the answer.

Is George Pullman really buried under steel and concrete? Was Walter Newberry buried in a rum barrel? And who is the Girl in Glass? Geoffrey Baer explores with Adam Selzer.

Why is there a mausoleum in Chicago’s Lincoln Park? Geoffrey Baer explores with Adam Selzer.

Was a UFO once spotted at O’Hare Airport? Geoffrey Baer heads out to the tarmac to investigate, with the help of the reporter who broke the story and Tom Skilling.

Salvador Dalí’s Visions of Eternity perplexed Art Institute of Chicago curators, who wondered if it was really Dalí’s work at all. Geoffrey Baer explores in this Chicago Mysteries digital exclusive.

Why is the shot-and-chaser combination of Malört and Old Style called a Chicago Handshake if its two ingredients aren’t from Chicago? Geoffrey Baer investigates this question and tries out Malort for himself in this Chicago Mysteries digital exclusive.

O'Hare's four terminals are numbered 1, 2, 3 and 5, but this wasn't always the case. Geoffrey Baer explains in this Chicago Mysteries digital exclusive.

Fluxus artist Wolf Vostell notoriously covered objects in concrete, but it’s unclear if there’s anything inside his Betonbuch, or Concrete Book. Geoffrey Baer explores in this Chicago Mysteries digital exclusive.