They may be at work pursuing the greatest mysteries of the physical world—yet the men and women who operate the world’s most prestigious physics and astronomy laboratories aren’t necessarily too busy to host guests. Throughout the world, physics and astronomy labs—many of them shimmering like stars in the wake of tremendous discoveries and achievements, some on mountaintops, others underground—welcome visitors to tour the premises, see the equipment, look through the telescopes and ponder just why they almost always make you wear a hardhat.

CERN. It’s the little things in life that really matter to the researchers at CERN, or the European Organization for Nuclear Research. This facility—located near Geneva, Switzerland—has gained superstardom over the last year, after announcing the discovery of what had been a holy grail of physics for decades—sometimes called the “God particle.” First predicted by physicist Peter Higgs in 1964, the then-theoretical particle, which pops from a field that is believed to give other particles their mass—became known as the Higgs boson before more recently assuming its grandiose nickname. CERN’s $10 billion atom smasher, called the Large Hadron Collider, had been at work for several years in its subterranean home in the Alps, beneath the French-Swiss border, colliding protons at high speeds before rendering what seemed to be evidence for the God particle in 2012. After a year of analyzing data, CERN researchers officially announced in March that it was all but certain: They’d captured a handful of real, honest-to-God Higgs bosons (visible only via a peak on a graph of data). Should you be in the charming Swiss countryside this summer, consider taking a guided tour of this most distinguished of the world’s great physics laboratories.

Did you know? CERN’s researchers helped develop the World Wide Web as a way to share data among scientists.

Gran Sasso National Laboratory. Bundle up, say goodbye to the Italian sun and take a tour of the austere bowels of one of the largest underground laboratories in the world. The Gran Sasso National Laboratory welcomes visitors, who get to see some of the world’s finest physicists in action as they work on a variety of experiments. The laboratory is located thousands of feet below ground, beside a freeway tunnel within Gran Sasso e Monti della Laga National Park, and as wolves, deer and foxes in the wild country above chase and gobble each other up in their timeless ways, scientists in the Gran Sasso lab are busy pursuing the puzzles of neutrino physics, supernovas and dark matter. As part of an ongoing joint project, the Gran Sasso lab receives neutrino beams fired from the CERN lab, some 500 miles away. By observing a pattern of oscillations in such beams, protected from interfering particles by rock and water, scientists have been able to prove that neutrinos do have mass. (Still wearing that hardhat, I hope?)

W. M. Keck Observatory. Some of the largest telescopes on Earth stand on the summit of Mauna Kea, the 13,800-foot volcano on the Big Island of Hawaii. These instruments—about eight stories tall and weighing 300 tons each—have allowed researchers to pursue the most vexing of the universe’s questions: How do solar systems form? How fast is the universe expanding? What is its fate? Visitors age 16 and older can tour the site at a fee of $192. The tours last a marathon eight hours and include transportation, dinner, hot drinks and hooded parkas—which few tourists ever even think of packing along to Hawaii. WARNING: The high altitude of the site can pose pressure-related health hazards, and SCUBA divers should not visit the Keck Observatory shortly after any significant time spent underwater.

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