Flagstaff, Arizona, is home to Lowell Observatory, one of the country’s most influential observatories. (It’s where Pluto was discovered, after all.) Lowell has been operating research telescopes since 1894—and still is—but the public is welcome in on the sky-charting fun, from the Giovale Open Deck Observatory to the brand-new Astronomy Discovery Center, which houses an on-site planetarium, a “universe theater,” and more.

The little green guys aren’t taken seriously in much of the world, but they are in Roswell, New Mexico. Home to the most famous alleged UFO crash in history, Roswell has put all its alien knowledge in one place: the International UFO Museum and Research Center. Offering guests a comprehensive look at extraterrestrial phenomena across the centuries and decades—and a few hilarious photo opportunities—it’s hard to leave here not wondering about the existence of life on other planets.

Orlando’s Kennedy Space Center Visitor Complex is as close as most of us will ever get to being an astronaut. This “museum” gives visitors access to two IMAX theaters, Launch Complex 39 (a rocket-launch site), the Shuttle Launch Experience (a ride simulator), astronaut training experiences, presentations from NASA astronauts, tons of fascinating exhibits, views of actual space shuttles, and more. Don’t rush this one—a solid half-day is needed to soak in all the excellent attractions here.

While you can’t (legally) get inside Area 51, Nevada does offer its alien-questing visitors a consolation prize: the Extraterrestrial Highway. Blast out of Las Vegas heading north on Highway 93, and you’re on the road. Look for the Little A’Le’Inn, E.T. Fresh Jerky, the famous “Black Mailbox,” the Alien Research Center, and even the Nevada National Security Site, which includes the Nevada Test and Training Range and, yes, the outskirts of Area 51.

High on the slopes of Mount Hollywood, just looking at Griffith Observatory is a delight. But there’s no reason not to go inside: Admission to this world-class celestial attraction is entirely free. Visitors get access to the historic observatory’s excellent exhibits—which include the chance to gaze through the Zeiss refractor telescope—live Tesla Coil demonstrations, astronomer talks, and more. Definitely come in the evening to catch the Hollywood views, a public star party, or both.

Chicago’s Adler Planetarium, on the shores of Lake Michigan, is America's first planetarium—and it’s arguably the country’s best. Visitors can explore the cosmos across three domed theaters, exhibits on space science, and collections that include the Gemini 12 space capsule, antique scientific instruments, and more. The onsite Doane Observatory offers a large telescope for public viewing, too. If you can, attend one of the Adler After Dark events, and live out your Night at The Museum dreams.

Yerkes Observatory dates back to 1895—though decidedly in Wisconsin, it was originally part of the University of Chicago. Today, visitors can only access the observatory via guided tour, which means all guests get a behind-the-scenes look at the Great Refractor, the world’s largest refracting telescope, and more (like the sleeping quarters of Hubble and Sagan). Keep an eye on their calendar—a few times a year, the observatory lets visitors gaze at the cosmos through the Great Refractor.

The history (and future) of human spaceflight is on display at Space Center Houston, aka the Official Visitor Center of the NASA Johnson Space Center. Home to more than 400 space artifacts, including the world’s largest public display of moon rocks and a rare sample of the Bennu asteroid, the site showcases actual rockets, a fabulous Mission Mars exhibit, and even Historic Mission Control, from which NASA led the Gemini and Apollo missions.

One of the most-visited museums in the country, Washington DC’s National Air and Space Museum is, essentially, America’s repository of all things spaceflight. Everything you see here is legit—not a reproduction—from Apollo 11 to Charles Lindbergh’s Spirit of St. Louis to the Wright Brothers’ flyer. There’s even the starship Enterprise, from Star Trek. In other words, if you can’t find something that fascinates you here, that’s a skill issue.