Mauna Kea Observatory—Hawaii, USA
13,796 feet above sea-level and isolated in the Pacific Ocean, the observatories at Mauna Kea on Hawaii's Big Island offer some of the most pristine star-gazing conditions in the world. Tourists can visit the summit, but officials suggest stopping at the Visitor's Center, located at 9,200 feet, before continuing onward (both to check weather conditions and acclimate to the elevation).
Every night of the year, from 6:00 pm to 10:00 pm. Mauna Kea offers stargazing and star tours to visitors, with telescopes available for amateur astronomers. It's completely free, and you don't need a reservation to participate.
(Part of our special report on Life in the Cosmos)
Very Large Array—Socorro, New Mexico, USA
Fans of the movie Contact will recognize the Very Large Array, a massive radio telescope facitilty located 50 miles west of Socorro, New Mexico. The site is open for self-guided tours from 8:30 am to sunset. On the first Saturday of each month, the facility holds free guided tours at 11:00 am, 1:00 pm and 3:00 pm. No reservations are required for the guided tours, which run 30 minutes.
Royal Observatory, Greenwich—London, U.K.
Home of the prime meridian, the Royal Observatory, Greenwich played a major role in the history of astronomy and navigation. Before the observatory was built, the grounds housed important buildings in English history dating all the way back to William I (the Tudors lived in Greenwich Castle, which was built on the same land as the Observatory).
The Royal Observatory and Planetarium features a museum with a wide variety of exhibits (including a number about astronomical navigation techniques), as well as London's only planetarium.
Cerro Paranal—Atacama Desert, Chile
Chile's Atacama Desert offers some of the most ideal stargazing conditions in the word: dry weather, cloudless skies, high altitude and little to no light pollution. To experience the best this stargazing oasis has to offer, check out the Paranal Observatory, located on the mountain of Cerro Paranal.
Operated by the European Southern Observatory, Paranal is home to The Very Large Telescope, a grouping of four very large telescopes (over 320 inches in diameter).
Guided tours of the observatory are offered to the public, without charge, every Saturday. Space is limited, so reservations are required.
Kitt Peak National Observatory—Arizona, USA
The American Southwest offers some of the best stargazing conditions in the United States—and perhaps none are more choice than Kitt Peak, a national observatory southwest of Tuscon, Arizona. Kitt Peak is home to the world's largest collection of optical telescopes, and offers guided tours daily at 10 am, 11:30 am and 1:30 pm. There are also nightly stargazing activities for those looking to peer at the cosmos through clear southwestern skies.
Griffith Observatory—Los Angeles, CA, USA
Sure, Los Angeles' polluted skies might not offer the best stargazing conditions, but a visit to the Griffith Observatory is as much about the history of Los Angeless as it is about the stars. The Griffith Observatory was donated to the city of Los Angeles in 1896; its first exhibit, in 1935, was the Foucault pendulum. It was also the location of two important scenes in Rebel Without a Cause.
The Griffith Observatory is open to visitors Tuesday through Sunday.
South African Astronomical Observatory—Sutherland, South Africa
At nearly 6,000 feet above sea level sits the South African Astronomical Observatory, or SAAO, an observatory famous for its pristine sky conditions due to altitude and minimal air pollution. Located about 230 miles inland from the South Atlantic Ocean, the SAAO offers visitors a chance to tour their facilities and see telescopes that have been in operation since the 1970s.
Visitors must call ahead and reserve space on a tour—the observatory offers two during the day, one fully guided (for 40 South African rands, or about $3.70) and one self-guided (for about $2.80). Night tours are also available Monday, Wednesday, Friday and Saturday, during which visitors can look at the night sky through telescopes 14" and 16" in diameter (larger than what most amateurs would have the opportunity to use.) Visitors cannot see any of the research telescopes during night tours, however.
Arcetri Astrophysical Observatory—Florence, Italy
If the hills of the Arcetri region of Florence were good enough for astronomy's ultimate bad boy (Galileo, maybe you've heard of him), then a visit to the Arectri Astrophysical Observatory, located in the very same hills where Galileo spent the last years of his life, should be good enough for you too. Arcetri Observatory doesn't boast the massive telescopes of Kitt Peak or radio technology like the Very Large Array, but it offers a chance to step back in time to a historic period in astronomy.
Daytime visits to the observatory are reserved for student groups, but nighttime visits are available for casual tourists. On Saturday evenings, the observatory holds an "Open Observatory," where groups of up to 5 visitors are welcome to explore the observatory and grounds.
Teide National Park—Island of Tenerife, Canary Islands, Spain
In 2013, the Starlight Foundation, which works to preserve clear night skies, named Teide National Park, located on the island of Tenerife in the Canary Islands, both a "Starlight Reserve" and a "Starlight Tourist Destination," thanks to its pristine night skies and ideal stargazing conditions. Laws exist on the island to control light pollution and flight pathways, in order to ensure perfect stargazing for visitors and astronomers alike.
Tenerife is the site of Starmus, a unique event that combines astronomy, art and culture. This year, Starmus will take place September 22-27.
Tenerife is also home to one of the world's most advanced observatories, the Teide Observatory. Interested travelers can schedule visits (for a minimum of 15 people) by contacting the observatory.
Hayden Planetarium—New York City, USA
It's an unfortunate reality for star lovers that it can't be perfect weather all the time—sometimes its cloud and rainy, thwarting chances of a perfect starry night. For times like that, head to the Hayden Planetarium in New York City. Here, you can take in an IMAX or Space Show, or check out one of the Rose Center for Earth and Space's four exhibits: the Cullman Hall of the Universe, the Big Bang Theater (which features a show about the Big Bang), the Heilbrunn Cosmic Pathway and the Scales of the Universe.
Tickets to the Rose Center for Earth and Space and the planetarium must be bought through the American Musem of Natural History; general admission tickets start at $22 and offer access to the Natural History Museum as well as the space exhibits.
(Part of our special report on Life in the Cosmos)