Chicago CNN  — 

At first glance, the building looks like others in downtown Chicago. Home today to Harry Caray’s Steakhouse, its exterior is punctuated by a bright neon sign; for fans of Major League Baseball and the restaurant’s namesake, this is a destination.

The restaurant walls are covered in MLB memorabilia and photos of everyone who’s visited, from the likes of actress Mila Kunis to former US President Barack Obama.

Though celebrities have graced these hallways the last few decades, there’s a deeper and darker history within these walls. If these walls could speak, they’d tell the tale of many a mob operation during the Al Capone era.

Built in 1895, the building sits on Chicago’s very first designated block; now one of more than 20,000.

In that time, it’s passed through multiple, often notorious owners and lived even more lives. It’s been a museum for taxidermy animals, a bootlegged liquor distribution center and housed illegal slot machines.

During Prohibition, it became a speakeasy owned by one of Al Capone’s cohorts, Gustav Muller. The location held a dual purpose back then. It was kitty corner to the Cook County Courthouse, which according to the Chicago Tribune, was a frequent haunt for the unwilling Capone.

When Capone’s reign of the Chicago underworld came to an end in 1931, his influence did not.

His right-hand man turned mob boss, Frank Nitti, a mobster known by the nickname The Enforcer, bought the building in 1939 and continued to use it to distribute liquor. The fourth floor became Nitti’s home.

Every floor of this four-story building has secrets.

The current owners of Harry Caray’s Steakhouse have been unearthing these secrets since taking over the building in 1987. More than three decades later, bricked-in walls are still giving way to hidden safes in the bowels of the building.

At basement level, it’s eerily quiet. Dark and dusty tunnels run the length the building, leading to what current restaurant owner, Grant DePorter, says was once Chicago’s vast underground tunnel system.

It’s in the same maze of rooms where DePorter discovered a safe, which once cracked open, contained Frank Nitti’s phone book – a veritable trove of information on all those in positions of power in Chicago at the time.

DePorter’s latest discovery, which was made in 2018, is a box behind a bricked-in wall. It’s one he has yet to excavate, but aims to do so soon. According to him, drilling holes and taking out bricks can be tricky.

More than 70 years after Al Capone’s death – remnants from his time are still being uncovered. And unknowing diners at Harry Caray’s Steakhouse are none the wiser.

Harry Caray’s Italian Steakhouse, 33 West Kinzie, Chicago; 312.828.0966. Visitors to the restaurant can visit a small collection of mob-related artifacts curated by the owners. There’s also a speakeasy – Nitti’s – nodding to the building’s mob roots.