In which US state would you find the Grand Canyon, one of the Seven Natural Wonders of the World? This massive canyon was carved by the Colorado River over 5-6 million years. It is 446 kilometers (277 miles) long, up to 29 kilometers (18 miles) wide, and over 1,800 meters (6,000 feet) deep. The rock layers exposed in the canyon walls record over 2 billion years of Earth's geological history. The average depth is 1,600 meters (1 mile). The canyon is so large that you could fit the entire country of Luxembourg inside it. About 6 million people visit each year, and the South Rim is open year-round. The canyon was declared a US National Park in 1919 and a UNESCO World Heritage site in 1979. The native Havasupai people have lived in the canyon for over 800 years.

The Victoria Falls, one of the Seven Natural Wonders, is located on the border of which two African countries? These waterfalls are 1,708 meters (5,604 feet) wide and 108 meters (354 feet) tall. The local name, "Mosi-oa-Tunya," means "The Smoke That Thunders" because the spray rises up to 400 meters (1,300 feet) and can be seen from 50 kilometers (30 miles) away. During the rainy season (April-May), over 500 million cubic meters of water flow over the falls every minute. A permanent rainbow can be seen at the falls. The explorer David Livingstone named them after Queen Victoria in 1855. The falls are a UNESCO World Heritage site and one of the most spectacular waterfalls on Earth. The surrounding rainforest is unique – it exists because of the constant spray from the falls.

On the border of which two countries would you find Mount Everest, the world's highest peak at 8,848 meters (29,029 feet)? The mountain was named after Sir George Everest, a British surveyor, in 1865. The Tibetan name is "Chomolungma" (Goddess Mother of the World) and the Nepali name is "Sagarmatha" (Goddess of the Sky). The first successful summit was by Sir Edmund Hillary (New Zealand) and Tenzing Norgay (Nepal) in 1953. Over 6,000 people have summited Everest, but over 300 have died trying. The most dangerous section is the "Death Zone" above 8,000 meters where oxygen is only 1/3 of sea level. Climate change is melting the Khumbu Icefall, making climbing more dangerous. The mountain grows about 4 millimeters (0.16 inches) per year due to tectonic plate movement.

Which country is home to the Great Barrier Reef, the world's largest living structure and a UNESCO World Heritage site? This massive reef system covers 344,400 square kilometers (133,000 square miles) and contains over 2,900 individual reefs and 900 islands. It is the only living structure visible from space. The reef is home to 1,500 species of fish, 400 species of coral, 4,000 species of mollusk, 240 species of birds, and 30 species of whales and dolphins. It also contains the world's largest population of dugongs (sea cows) and six of the world's seven species of sea turtles. The reef is under threat from coral bleaching caused by rising ocean temperatures. The Australian government has committed over 3 billion dollars to protect it. It generates 6.4 billion dollars in tourism revenue annually.

In which region of the world would you have the best chance of seeing the Aurora Borealis (Northern Lights)? This natural light display occurs when charged particles from the sun collide with atoms in Earth's atmosphere. The best viewing locations are within the "auroral oval" around the magnetic North Pole, typically between 65° and 72° latitude. The best months to view are from September to March during dark, clear nights. The most active years for the Northern Lights follow an 11-year solar cycle – the next peak is 2025. Colors come from different gas particles: green (most common) from oxygen, red from high-altitude oxygen, and purple/blue from nitrogen. The lights are also visible in the Southern Hemisphere, where they are called Aurora Australis (Southern Lights).

In which country did the Parícutin Volcano suddenly appear in a farmer's cornfield in 1943, becoming one of the Seven Natural Wonders? This volcano is unique because scientists were able to witness its entire life cycle from birth to extinction. On February 20, 1943, farmer Dionisio Pulido saw his cornfield begin to smoke and crack open. Within 24 hours, a 50-meter (164-foot) cone had formed. By the end of the first week, it was 150 meters (492 feet) tall. Over 9 years, the volcano grew to 424 meters (1,391 feet) and buried two villages (Parícutin and San Juan Parangaricutiro) – only the church steeple of San Juan remains visible above the lava. The eruption ended in 1952. The volcano is now dormant and a popular tourist attraction. It was named one of the Seven Natural Wonders in 1997.

Which Brazilian city is home to the natural wonder known as the Harbor of Rio de Janeiro (Guanabara Bay), one of the largest natural bays in the world? This bay is surrounded by granite monoliths, including Sugar Loaf Mountain (Pão de Açúcar) and Corcovado Mountain (home to the Christ the Redeemer statue). The bay was first discovered by Portuguese explorer Gaspar de Lemos in 1502. It is 31 kilometers (19 miles) long and 28 kilometers (17 miles) wide. The bay contains over 130 islands, including Governor's Island where the international airport is located. The unique geology was formed by erosion of granite mountains. Portuguese explorers thought the bay was the mouth of a great river (hence the name "Rio de Janeiro" – River of January). The bay is a UNESCO World Heritage site and was named one of the Seven Natural Wonders of the World.

The spectacular Iguazu Falls, a UNESCO World Heritage site and candidate for the Seven Natural Wonders, is located on the border of which two countries? This waterfall system consists of 275 individual drops along 2.7 kilometers (1.7 miles). The tallest drop, called the "Devil's Throat" (Garganta del Diablo), is 82 meters (269 feet) high. The name "Iguazu" comes from the Guarani words "y" (water) and "guasu" (big). According to legend, a god planned to marry a beautiful woman named Naipí, but she fled with her mortal lover Tarobá in a canoe. The god became enraged and sliced the river, creating the falls and condemning the lovers to an eternal fall. The falls are wider than Victoria Falls and taller than Niagara Falls. Visitors can see the falls from both countries, connected by footbridges.

Why can people float effortlessly in the Dead Sea without any effort? The Dead Sea, located between Israel and Jordan, is actually a salt lake – the saltiest body of water on Earth (excluding small hypersaline lakes). Its salinity is 34.2%, compared to the ocean's 3.5% – about 10 times saltier. The high salt content makes the water much denser than fresh water or regular seawater, providing greater buoyancy. It is nearly impossible to sink – you float like a cork. The Dead Sea is also the lowest point on Earth's surface (excluding ocean depths) at 430 meters (1,412 feet) below sea level. The water contains 21 different minerals, including magnesium, calcium, and potassium. The high mineral content makes the water look oily and feel slippery. You cannot swim in the Dead Sea – only float.

Which country is home to Jeju Island, a volcanic island known for its lava tubes, Hallasan Mountain, and being called the "Island of the Gods"? This island was formed by volcanic eruptions about 2 million years ago. Hallasan Mountain is the highest point in the country at 1,947 meters (6,388 feet) and is a dormant volcano. The island has a unique system of lava tubes – Geomunoreum Lava Tube System is a UNESCO World Heritage site. The island is famous for its "haenyeo" (female divers) who free-dive to collect seafood without oxygen tanks – a tradition dating back 1,000 years. The island has 368 parasitic cones (oreums) around Hallasan. It is a popular honeymoon destination and has been called the "Hawaii of [the country]." The island was named one of the New Seven Natural Wonders in 2011.