11 things you can only experience in Chicago

On a clear day, you can see up to four states from the Willis Tower Skydeck, set atop the 103rd floor of one of Chicago's most famous skyscrapers. But for truly breathtaking views, you'll want to step inside The Ledge—a set of glass boxes that jut out over the edge of the building, allowing guests to look down on the streets and structures below. If you're brave enough to stand on a floor made of (very thick) glass, you might feel like you're floating 1,353 feet above the ground.

You've probably seen a Tyrannosaurus rex skeleton before, but unless you've been to the Field Museum, you haven't seen the world's most complete specimen. After years of greeting visitors in the museum's main hall, SUE the T. rex now resides in the "Evolving Planet" exhibition, in its own personal room. When scientists discovered the skeleton, 90 percent of the bones were intact—and at 40 feet long, SUE is the largest T. rex that researchers have found. Did we mention that SUE has a Twitter account?

You can't miss the dazzling marquee at the Green Mill, a jazz club in Uptown that dates back to 1907 and was once part of a sprawling entertainment complex that occupied an entire city block. During Prohibition, the Green Mill was famously a mob hangout and was purportedly co-owned by "Machine Gun" Jack McGurn. Notorious gangster Al Capone was a regular and always sat in a curved booth near the bar, where he could keep an eye on the front and back doors. There's also a hidden trap door leading to a tunnel used for quick escapes—but don't even bother asking for a tour.

Why settle for a single ice cream flavor when you could have five? The Original Rainbow Cone in Beverly has been serving cones stacked with its signature combo of chocolate, strawberry, Palmer House (vanilla with cherries and walnuts), pistachio and orange sherbet for more than 80 years. Head to the far South Side stand, visit the Navy Pier outpost or find the Rainbow Cone ice cream truck to get a taste of this sweet treat.

You can see Frank Lloyd Wright-designed buildings like the Robie House and the Emil Bach House without leaving city limits, but a ride on the Green Line to Oak Park will allow you to see 25 structures credited to the famous architect. Start at the Frank Lloyd Wright Home and Studio and take a self-guided walking tour of the neighborhood, which boasts more Wright buildings (many exhibiting his signature Prairie style) than anywhere in the world. Check out the Frank Lloyd Wright Trust for information about guided tours.

Wrigley Field and Fenway Park are the two oldest Major League Baseball stadiums in the country—Fenway is two years older than Wrigley—and the two ballparks are also home to the last remaining manually operated scoreboards. The one on the Cubs' home turf sits atop the bleachers, separating it from Boston's, which is located at ground-level in left field. It takes a staff of three employees to keep the numbers up-to-date during each Cubs game, hauling seven-pound steel plates through the narrow three-story structure.

The World's Columbian Exposition of 1893 was one of the biggest events ever held in Chicago—unfortunately, most of the infrastructure created for the fair was designed to be temporary. One building that did survive was the Palace of Fine Arts, which was rebuilt in 1933 as the Museum of Science and Industry. Visitors can also walk through Jackson Park to see where many of the pavilions created for the event were located and head to the intersection of Hayes and Richards drives to peep a scaled-down replica of the Statue of the Republic that once overlooked the Exposition.

In 1949, Illinois salesman Ed Seymour put a mixture of paint and aerosol in a can at the suggestion of his wife (he needed a quick way of touching up radiators) and spray paint was born. Today, artists throughout the city put the Seymours' invention to use, brightening walls with colorful creations—most notably on a stretch of 16th Street in Pilsen. Taking over the side of a railroad embankment between Chicago River to Western Avenue, you can walk through an outdoor gallery featuring work by local artists and international talent.

Long before he became President of the United States, Barack Obama met his wife-to-be Michelle while the two were working at a Chicago law firm. Before they had their first official date, the couple shared their first kiss while eating ice cream on the curb outside of a Baskin-Robbins in Hyde Park. The building at the corner of 53rd Street and South Dorchester Avenue now houses a Subway, but you'll find a rock with a plaque depicting Barack and Michelle kissing in front of the shopping center.

The Chicago River is typically a muddy shade of brown-ish blue, but for one day each year it's emerald green. As an annual tradition, the Journeymen Plumbers Local Union 130 dyes the river just before the city's St. Patrick's Day Parade in Grant Park, drawing crowds of onlookers who gather on bridges and either side of the river to observe the ceremony. The dye is vegetable-based, so it doesn't muck up the city's most prominent waterway, and the color usually only sticks around for 24 hours at most before fading.

Pizzeria Uno famously served the first deep dish pizzas in the 1940s from its original River North location, cementing the thick, cheesy take on the Italian dish as a Chicago staple. Decades later, we're still eating deep dish (from time to time, usually when friends are in town) at pizzerias across the city. If you want to try one of the best pies in town, head to Art of Pizza—an old-school parlor with locations in the Loop and Lakeview. Just make sure you show up hungry!