This is one of the hottest museum tickets in town, thanks to the $210 million Rose Center for Earth and Space, whose four-story-tall planetarium sphere hosts the excellent Harrison Ford-narrated Space Show, "Are We Alone?," the most technologically advanced sky show on the planet. Prepare to be blown away. The show is short -- less than a half hour from start to finish -- but phenomenal. (New York magazine has called it "the world's largest, most powerful virtual-reality simulator.")

Buy your tickets in advance for the Space Show in order to guarantee admission (they're available online); you can also buy tickets in advance for a specific IMAX film or special exhibition, such as the Butterfly Conservatory, which I recommend, especially during peak seasons (summer, autumn, holidaytime) and for weekend visits; otherwise, you might miss out.

Start your tour of the museum at the Rose Center with the Space Show. Afterwards, follow the wondrous interactive Cosmic Pathway, which spirals around the sphere and down to the main level, chronicling the 15-billion-year evolution. (The sphere itself is even used to create a point-of-reference scale that puts the universe into better perspective than the entire semester I spent in undergrad astronomy.) Other must-sees include the Big Bang Theater, which re-creates the theoretical birth of the universe; the main Hall of the Universe, with its very own 15 1/2-ton meteorite; and the terrific Hall of Planet Earth, which focuses on the geologic processes of our home planet (great volcano display!). All in all, you'll need a minimum of 2 hours to fully explore the Rose Center. Tip: Friday night is a great time to plan your visit, as the center isn't overcrowded, live jazz and food fill the Hall of the Universe, and, bathed in blue light, the sphere looks magical.

The rest of the 4-square-block museum is nothing to sneeze at, either. Founded in 1869, it houses the world's greatest natural science collection in a square-block group of buildings made of towers and turrets, pink granite and red brick -- a mishmash of architectural styles, but overflowing with neo-Gothic charm. The diversity of the holdings is astounding: some 36 million specimens ranging from microscopic organisms to the world's largest cut gem, the Brazilian Princess Topaz (21,005 carats). Rose Center aside, it would take you all day to see the entire museum, and then you still wouldn't get to everything. If you don't have a lot of time, you can see the best of the best on free highlights tours offered daily every hour at 15 minutes after the hour from 10:15am to 3:15pm. Free daily spotlight tours, thematic tours that change monthly, are also offered; stop by an information desk for the day's schedule. Audio Expeditions, high-tech audio tours that allow you to access narration in the order you choose, are also available to help you make sense of it all.

If you only see one exhibit, see the dinosaurs, which take up the entire fourth floor. Start in the Orientation Room, where a short video gives an overview of the 500 million years of evolutionary history that led to you. Continue to the Vertebrate Origins Room, where huge models of ancient fish and turtles hang overhead, with plenty of interactive exhibits and kid-level displays on hand to keep young minds fascinated. Next come the great dinosaur halls, with mammoth, spectacularly reconstructed skeletons, and more interactive displays. Mammals and Their Extinct Relatives brings what you've learned in the previous halls home, showing how yesterday's prehistoric monsters have evolved into today's modern animals. Simply marvelous -- you could spend hours in these halls alone.

The Hall of Biodiversity is an impressive multimedia exhibit, but its doom-and-gloom story about the future of rain forests and other natural habitats might be too much for the little ones. Kids 5 and up should head to the Discovery Room, with lots of hands-on exhibits and experiments. (Parents, be prepared: There seems to be a gift shop overflowing with fuzzy stuffed animals at every turn.)

The museum excels at special exhibitions, so check to see what will be on while you're in town in case any advance planning is required. The magical Butterfly Conservatory, a walk-in enclosure housing nearly 500 free-flying tropical butterflies, has developed into a can't-miss fixture from October through May; check to see if it's in the house while you're in town.