The Willis Tower, originally and still commonly referred to as the Sears Tower, is a 110-story, 1,451-foot skyscraper designed by architect Bruce Graham and engineer Fazlur Rahman Khan of Skidmore, Owings & Merrill (SOM). It opened in 1973 as the world's tallest building, a title that it held for nearly 25 years. It is the third-tallest building in the Western Hemisphere, as well as the 23rd-tallest in the world. Each year, more than 1.7 million people visit the Skydeck observation deck, the highest in the United States, making it one of Chicago's most popular tourist destinations. Depending on the day of the week, tickets for the Skydeck range from $32 to $44.

The Griffin Museum of Science and Industry is a science museum housed in the Palace of Fine Arts from the 1893 World's Columbian Exposition. Among the museum exhibits are a full-size replica coal mine, a German submarine U-505 captured during World War II, a 3,500-square-foot model railroad, the command module of Apollo 8, and the first diesel-powered streamlined stainless-steel passenger train (Pioneer Zephyr). Ticket prices start at $25.95.

For more than 25 years, the CACs expertly trained docent volunteers have led the CAC River Cruise, sharing fascinating stories behind more than 50 buildings along the Chicago River. Hear how Chicago grew from a small settlement into one of the world's largest cities in less than 100 years. In just 90 minutes, you'll get the best overview of Chicago’s architecture and its history. Tickets start at $54.

The Field Museum is a natural history museum founded in 1894 to display exhibits and collections from the World’s Fair. It is named after its first major benefactor, Marshall Field, the department-store magnate, and is one of the largest natural history museums in the world. The permanent exhibitions include fossils, cultural exhibits from around the world, and interactive programming demonstrating today's urgent conservation needs. One of the most famous fossils in the Field Museum is Sue, the Tyrannosaurus Rex. Tickets start at $30.

The Adler Planetarium is a public museum dedicated to astronomy and astrophysics. It was founded in 1930 by local businessman Max Adler. The Adler has three theaters, space science exhibitions, including the Gemini 12 space capsule, and a collection of antique scientific instruments and print materials. There are a variety of different shows and exhibits to view. Tickets start at $25.

Shedd Aquarium is an indoor public aquarium that opened in 1930. The 5 million US gallon aquarium holds about 32,000 animals and is the third largest aquarium in the Western Hemisphere. Shedd Aquarium partners with various organizations around the world to help rescue and rehabilitate wildlife in need as well as protect endangered species and their habitats. Tickets start at $44.95.

The Art Institute of Chicago, founded in 1879, is one of the oldest and largest art museums in the United States. Its collection, stewarded by 11 curatorial departments, includes works such as Georges Seurat’s A Sunday on La Grande Jatte, Pablo Picasso’s The Old Guitarist, Edward Hopper’s Nighthawks, and Grant Wood’s American Gothic. Its permanent collection of nearly 300,000 works of art is augmented by more than 30 special exhibitions mounted yearly. Tickets start at $32.