Welcome to 40 Under 40: Places—40 of the most important, most interesting, and quirkiest American places less than 40 years old, compiled by the staff of Preservation magazine. The by-no-means comprehensive list includes sites both well-known and obscure, high-end and low-budget, and urban and rural. Places typically aren’t considered historic until they’ve been around for at least 50 years, so why highlight younger sites now? Because by looking at them through a preservation lens and identifying places worthy of saving BEFORE they become truly historic, we can be proactive about their futures.

Each place on our list was built in 1978 or later, and each makes an important contribution in one of six categories: Arts, Science and Tech, Culture, History, Landscape, and Housing. We’ll be rolling out our 40 Under 40 Places stories, category by category, through the end of 2018, and a public online voting period will take place from January 7-18, 2019. Top vote-getters will be featured in the Spring 2019 issue of Preservation. Read on to see if any of your favorite places made our list—and please vote for your top choices in January!

Related stories: Arts, Culture, Landscapes

Here are the six places on our list from the Science and Tech category.

Biosphere 2—Oracle, Arizona (pictured above)

Many associate Biosphere 2, the largest self-contained ecosystem ever created, with its infamous 1990s experiments, in which eight people were sealed inside for a planned two years. The goal was to study the delicate relationship between humans and the environment, with its potential applications to space colonization as a secondary objective.

But Biosphere 2 is much more than a site of historical interest. Built in 1991 and operated by the University of Arizona since 2007, it has since become the definitive facility for scientists to study the effects of environmental changes, human-caused and otherwise, on a real-world scale.

Seven biomes—including a tropical rainforest, fog desert, and ocean—are spread out over three acres, now separated to run controlled experiments. At the ocean system, for example, coral reefs are exposed to changing water temperature and pH levels to reflect the anticipated effects of climate change, in hopes of selectively breeding more resistant individual coral. And at the Landscape Evolution Observatory area, a repurposed agricultural zone, three 1,000-ton hill slopes are used to simulate watersheds, testing (among many other things) the effect of land usage on water quality further downstream.

The facility is open to the public for tours, and nearly 100,000 visitors pass through its doors every year.

Location: 32540 S. Biosphere Road, Oracle, AZ 85623

Hours: Daily, 9:00 a.m. to 4:00 p.m.

Fun Fact: Despite its name, Biosphere 2 has no predecessor—the first biosphere being alluded to is Earth itself.

Desert Dome—Omaha, Nebraska

The largest indoor desert in the world, the Desert Dome at Omaha’s Henry Doorly Zoo and Aquarium is both an architectural and biological marvel. Rising 13 stories into the air, the geodesic dome itself is also the largest of its kind in the world, made up of 1,760 glazed acrylic panels. Over 500,000 pounds of steel and 10,000 tons of concrete help support the structure.

Under the dome, 84,000 square feet of exhibit space spread over two floors (the lower floor is home to “Kingdoms of the Night,” the world’s largest nocturnal exhibit) showcase flora and fauna from three deserts around the globe: Africa’s Namib Desert, the Red Center of Australia, and the Sonoran Desert of the Southwestern United States. Collared pecarries, central bearded dragons, and death adders are just a few of the exotic species you can find inside. A 55-foot mountain sits at the dome’s center, dividing the deserts.

After three years of construction, the $31.5 million dome opened in March of 2002. It remains a vital feature of the zoo, which is the most-visited attraction in the state of Nebraska.

Location: 5701 S. 10th Street, Omaha, NE 68107

Hours: Daily, 10:00 a.m. to 4:00 p.m. through March 14

Fun Fact: Each of the dome's panels are tinted one of three different shades, helping conserve energy and regulating the amount of sunlight entering the dome.

Googleplex—Mountain View, California

As the headquarters of one of the world’s most ubiquitous tech companies, it’s no surprise that the Googleplex has become a cultural landmark. Immediately recognizable by its Android statues, T-Rex skeleton replica, and multicolored bicycles, it’s an essential destination on any tourist’s Silicon Valley itinerary.

But perhaps the most notable aspect of the complex is its campus-like design, innovative for its time. After Google leased the property from computing manufacturer Silicon Graphics in 2004 (eventually purchasing it in 2006), they soon began exploring ways to optimize their new workspace, holding a design competition. The winner, Clive Wilkinson Architects, sold Google on their vision of a self-contained complex that accommodated both private and collaborative work—much like a university. By encouraging employees to work how they wanted and removing their need to leave campus, Clive Wilkinson hoped to create a space that maximized productivity and innovation.

The resulting work environment has many pros and some cons, but it is undoubtedly one of the most unique and iconic office complexes in the world. Even as the field of technology continues to expand and evolve, one can expect that the Googleplex will evolve right along with it.

Location: 1600 Amphitheatre Parkway, Mountain View, CA 94043

Hours: Daily (campus only, interiors of most buildings off-limits)

Fun Fact: Clive Wilkinson Architects designed 13 individual work settings ranging from "hot" to "cold" (public to private), which were integrated into each building on campus.

Mike O'Callaghan-Pat Tillman Memorial Bridge—Nevada/Arizona

For decades, government officials and engineers had envisioned a bridge that could divert car traffic from the Hoover Dam, overburdened as the region’s primary crossing of the Colorado River. However, the challenge of building a structure that could withstand the winds of the Black Canyon (and securing the funds to do so) had stymied all previous attempts.

Enter the Mike O’Callaghan-Pat Tillman Memorial Bridge, the highest arched concrete bridge in the Western Hemisphere. Incorporating the world’s widest concrete arch, the 1,900-foot-long bridge was completed in October of 2010 after five years of construction. In addition to providing safer passage across the canyon, the installation of the bridge 1,500 feet south of the Hoover Dam also allowed for several dangerous hairpin turns and curves elsewhere in the route to be removed.

David Goodyear of T.Y. Lin International designed it not only with high winds in mind, but also potentially destructive earthquakes. He settled on a twin-ribbed arch for added stability, with prefabricated concrete columns connecting the bridge to the cliffs below. In all, the design and construction of the bridge cost $240 million in federal and state funds and bonds.

Location: Hoover Dam, NV

Hours: Daily

Fun fact: The bridge’s name honors individuals from both Nevada and Arizona, the two states which it connects. One was a former governor of Nevada, while the other was an NFL player who left sports to join the U.S. Army before being killed by friendly fire in 2004.

Tilikum Crossing—Portland, Oregon

When you come to Tilikum Crossing, Bridge of the People, something might seem unusual—namely, the lack of any cars. That, of course, is entirely by design. Tilikum Crossing opened in September of 2015, becoming the first major bridge in the country to be designed for people and public transportation, but not cars.

Traversing the Willamette River, the 1,720-foot-long bridge consists of four separate “lanes”: two in the middle for buses and trains, with a pedestrian-and-cyclist pathway on either side. Cables strung through the bridge’s two 180-foot towers support its deck. Designed by San Francisco-based architect Donald MacDonald and David Goodyear of T.Y. Lin International, its name comes from the Chinook Jargon word for “people” and “relatives,” honoring the indigenous tribe. It is owned by TriMet, the city of Portland's mass transit agency. By encouraging alternative forms of transportation, Tilikum Crossing helps pave the way forward to a greener, more sustainable future.

Location: Tilikum Crossing, Portland, OR 97201

Hours: Daily

Fun Fact: Over 175 LED lights adorn the bridge’s cables and towers. The colors and pace at which they appear to move across the bridge reflect the real-time water temperature and speed of the Willamette River.

Very Large Array—Socorro County, New Mexico

You may or may not know that ice has been found in deep craters on the planet Mercury, or that the supermassive black hole sitting at the center of our galaxy likely formed before the galaxy itself. However, these discoveries of astronomic proportions would not have been possible without the Karl G. Jansky Very Large Array (VLA), located in central New Mexico.

Consisting of 27 powerful radio dishes arranged in a distinctive “Y” shape, the VLA was constructed throughout the 1970s and formally dedicated in 1980. Combined, the dishes’ antennae create a single telescope capable of picking up radio signals millions of light years away. The 82-foot-diameter dishes are placed on rails and can be spread out as far as 23 miles, allowing astronomers to look deeper into space. Each one contains 10 receivers that are supercooled with helium gas to a constant -432 degrees Fahrenheit to prevent its own signals from interfering.

Over 3,000 researchers from around the world have used data from the VLA in 11,000 different projects, and that number continues to rise. In both the present and the future, the VLA will remain an invaluable tool in helping us to better understand the cosmos.