Chicago,illinois, or the "Windy City" is the third most-populated state in the U.S. and home to one of the largest metropolitan areas in the country. Chicago has a thriving tourism industry and several attractions that visitors must see. Buy a CityPass and you can see five of some of the following attractions for $84. If you're planning on visiting Chicago, here are several attractions that you don't want to miss.

Art Institute of Chicago

This is one of the world's great art museums, with collections dating from 3,000 B.C to the present. It contains the country's best collection of Impressionist and Postimpressionist paintings and drawings, fine and decorative arts from almost every continent, photography, textiles and architectural work. The museum also hosts numerous series of films, lectures and special presentations. Admission is inexpensive, but is free on Thursday evenings.

Millennium Park

Millennium Park is a relatively new tourist attraction, completed in 2004, that draws in both tourists and locals. It is just north of the Art Institute of Chicago. At the Jay Pritzker Pavillion, hundreds of concerts and performances are put on for audiences throughout the year. In the park, you can also find the large polished-steel sculpture known as "The Bean," or Cloud Gate, that people can walk right up to and touch. The park also contains a 5-acre garden and twin 5-foot towers that project images of people spitting out water, which comes out in a real fountain stream.

Museum of Science and Industry

This museum is a great place for families to bring their kids. It is the largest science center in the Western hemisphere, with over 2,000 exhibits, and it was the first museum in North America to offer interactive exhibits that visitors can touch. You can do things like make a giant heart beat in time with yours, have a virtual instructor guide you on the basketball court, and open a model Chicaco River drawbridge for a toy train. They also have a real jet, a real coal mine, and a passenger train that you can walk through. The museum is a little ways away from central Chicago, but it is one of the most visited attractions in the city.

The Magnificent Mile

The Magnificent Mile follows Michigan Avenue, starting at the Chicago River and heading north to Oak Street. It contains a mile worth of architecture, shopping restaurants, and businesses. It is a mecca for tourists and business people.

Navy Pier

This has been a Chicago landmark sick it opened in 1916. The pier takes up 50 acres of lakefront land. Here you can find several places to shop, eat, and stay entertained. It is home to the Chicago Children's Museum, an IMAX theater, an indoor botanical garden, the Chicago Shakespeare Theater, the Smith Museum of Stained Glass windows, a Ferris wheel, a fun-house, mini-golf, and more. This landmark attracts millions of people a year. Visitors can also catch fireworks twice a week in the summer.

Shedd Aquarium

The John G. Shedd is the world's largest indoor aquarium and Chicago's most visited cultural attraction. It houses more than 22,000 aquatic animals in more than 80 habitats. Visitors can even see large animals such as dolphins and whales and a 360-degree view of a Caribbean Reef. The only downside is that tickets are pricey at $25 a pop.

Skydeck Chicago

The skydeck is located on the 103rd floor of the Willis (Sears) Tower, which is the tallest building in the Western Hemisphere. On a clear day, visitors can see as far as Michigan, Wisconsin, and Indiana. The observation floor also features exhibits like Knee-High for kids, a 4-foot exhibit that contains cutouts of famous Chicagoans. The braver souls can step out onto The Ledge, a suspended glass enclosed balcony, which is 1,353 feet above the city. The Skydeck attracts 1.3 million a people a year and security can be tight, so plan extra time for this attraction.

The Field Museum

This natural history museum was chosen as the home case for fictional archaeologist, Indiana Jones. The museum's grand Stanley Field Hall is home to Sue, the world's largest, most complete, and best-preserved Tyrannosaurus Rex. Visitors can also find several preserved animal collections, rock and fossil collections, precious stones, and much more through the many exhibits.

John Hancock Observatory

This attraction is located in the third-tallest building in Chicago, right in the heart of the city's tourist district. The building is home to the fastest elevators in North America that zoom up to the 94th floor in 40 seconds. Through this open-air Skywalk, guests can spot Chicaco landmarks like Wrigley Field, Navy Pier, and much more with an impressive panoramic view. They can also enjoy a multimedia Sky Tour. Guests can also get this view from the Signature Room bar and even the 95th floor ladies room, without having to pay the observatory entrance fee.

Wrigley Field

Sport fans will enjoy the historic feel of this Chicago landmark. Wrigley Field is one of America's smallest, oldest, and best-love ball parks. Head there in the spring or summer and catch the Chicago Cubs play a game.