1. ...collection of Impressionist paintings.
(Outside the Louvre, that is!) In fact, the Art Institute's entire Department of Modern and Contemporary Art is considered one of the most comprehensive in the world. Among its holdings: late Water Lilies by Claude Monet, works by Picasso, and paintings by Henri Matisse.

2. ...contemporary art museum.
With a membership that surpasses the 15,000 mark, the Museum of Contemporary Art is on a mission to collect, preserve, and interpret the art of our time. The MCA documents contemporary visual culture through painting, sculpture, photography, video, film, and performance.

3. ...convention facility.
McCormick Place has over 2.2 million square feet of space. It also has 8 restaurants, 25 concession stands, 122 restrooms, some 700 pay phones, and a 1000-seat outdoor terrace.

4. ...dental library.
The American Dental Association is the accrediting agency for 1,242 dental educational and dental auxiliary educational programs in the United States. Its library has approximately 33,000 books and 17,500 bound journal volumes.

5. ...futures and options marketplace.
The Chicago Board of Trade.

6. ...indoor aquarium.
The Shedd, also known as "The World's Aquarium," is a non-profit institution committed to the conservation of aquatic life and its environments. Its Oceanarium is the world's largest indoor marine mammal pavilion.

7. ...manufacturer of chewing gum.
The Wm. Wrigley Jr. Company is well-known in Chicago not only because of its chewing gum, but also because it is the owner of the Wrigley Building and because it was the original owner of those "lovable losers," the Chicago Cubs.

8. ...public library.
The 756,640 square foot Harold Washington Library Center, opened in 1991. The nine-floor library has five-story-tall arched windows. It also has a Lower Level which contains a 385-seat paneled auditorium, an exhibit hall, and a video theater.

9. ...Tiffany Dome.
The Chicago Cultural Center (the first free, municipal cultural center in the US), recently celebrated its 100th anniversary. Originally built as the city's first permanent public library, its beaux-arts style features two spectacular stained-glass domes as well as intricate, coffered ceilings.

10. ...Tyrannosaurus Rex skeleton.
Discovered in 1990 in the badlands of New Mexico, Sue, is not only the largest but also the most complete T. Rex skeleton ever discovered. She is 42 feet long, with a five feet skull... and a brain cavity that is just big enough to hold a quart of milk.

Other big things in Chicago: