The first fortifications in what would become known as the Great Wall of China were built in the fifth century BCE, and work continued intermittently for several centuries thereafter. But it was the Ming Dynasty that made the wall what it is today. During the 14th to 17th centuries, rulers ordered the addition of fortresses and gates, and divided the structure into inner and outer walls to protect their cities.

Since 1991, the Great Man-Made River has brought fresh water from deep underneath the Sahara Desert to the coastline of Libya through a series of underground pipelines. The water originates from the Nubian Sandstone Aquifer System, which is a reservoir of "fossil water" discovered in the 1950s. The system provides necessary drinking water and irrigation for Libyan farmland.

Located in China's Hubei province and spanning the Yangtze River, the Three Gorges Dam generates 22,500 megawatts of energy, making it the largest hydroelectric facility in the world. The dam required 510,000 tons of steel to construct, and is so large that it can slow the rotation of the Earth when at full capacity.

Also known as the Pharos of Alexandria, this ancient lighthouse was completed around 280 BCE during the reign of Pharaoh Ptolemy II. At 350 feet, it was likely the tallest human-made structure in the world at the time besides the Pyramids at Giza. Though no longer standing, it's considered one of the Seven Wonders of the Ancient World.

The Segovia Aqueduct was built under the Roman emperor Trajan (98 to 117 CE) and is one of the best-preserved examples of the empire's groundbreaking aqueduct system. This particular aqueduct is still in use and carries water from the Frío River into the city over its 10-mile span. The aqueduct was named a UNESCO World Heritage Site in 1985.

Passing across eight time zones, 87 towns, and 16 rivers, the Trans-Siberian Railway is the longest passenger train journey in the world. The railway features three routes allowing passengers to access Russia, Mongolia, and China. It took 60,000 workers more than 25 years (from 1891 until 1916) to complete the project.

In 1956, President Dwight D. Eisenhower signed one of the most ambitious public works projects into law, the Federal Highway Act. This feat of engineering added more than 47,000 miles of roadway across the United States, and provided both ease of travel for American citizens as well as strategic military benefits.

New York City has been home to several of the world's tallest buildings, including the 791-foot-tall Woolworth Tower, which held the honor from 1913 until 1930. It was overtaken by the Chrysler Building until 1931, followed by the Empire State Building for the next four decades. The current record holder is Dubai's Burj Khalifa at 2,717 feet tall.

Completed in 2022 and connecting the city of Lapeseki on the Asian side of Turkey to Sütlüce on the European side, the 1915 Çanakkale Bridge measures 15,118 feet in total length. It also has the longest main span of any suspension bridge at 6,637 feet between the supporting towers. Previously, those records were held by Japan's Akashi Kaikyo Bridge.

Ghana's Lake Volta spans 3,283 square miles, accounting for 3.6% of the country's total land area. It is the largest artificial reservoir in the world by surface area. Measured by total volume, the largest human-made lake is Zambia's Lake Kariba, containing around 47.5 trillion gallons of water (compared to Volta's 39 trillion gallons).

The Bailong Elevator is located in Hunan, China, within the Zhangjiajie National Forest Park (which served as inspiration for the movie "Avatar"). With a name translating to "Hundred Dragons Elevator," the structure opened in 2002 and rises 1,070 feet tall, making it the world's tallest outdoor elevator. It offers breathtaking views of the surrounding mountains and forest.

Nicknamed "The Bird's Nest," the Beijing National Stadium — built for the 2008 Summer Olympics — is the world's largest steel structure. The arena used 110,000 tons of steel during construction, though the steel serves no practical purpose and is entirely decorative. Originally, the steel was added to support a stadium roof, though the roof was cut from the final design.

Finished around 2570 BCE and rising 481 feet above the ground, the Great Pyramid of Giza was the world's tallest structure until 1221 CE, when it was overtaken by Old St. Paul's Cathedral in London, England. Churches and cathedrals would remain the world's tallest buildings until completion of the Washington Monument in 1888.

Not to be confused with the aforementioned highest bridge, the Millau Viaduct is the world's tallest bridge (a measurement of its actual structural height). Shooting up to 1,104 feet, the viaduct is located in Creissels, France, and spans the Tarn Valley. It's 62 feet taller than another groundbreaking feat of French engineering, the Eiffel Tower.

China's Duge Beipanjiang Bridge stands a dizzying 1,854 feet above the Beipan River below, earning it the distinction of being the world's highest bridge. Engineers were forced to raise the bridge even higher than initially intended to avoid cracking in the brittle mountain limestone, and it was finally completed in 2016. It now connects China's Guizhou and Yunnan provinces.

Designed to ease Boston's congested traffic, the "Big Dig" took 25 years from start to finish and cost an estimated $24.3 billion, the most expensive highway project in U.S. history. The result of the Big Dig was a massive restructuring of Boston's highway system, which in turn lowered the city's carbon emissions by 12% upon its completion.

The groundbreaking Panama Canal opened its waterways in 1914, greatly reducing the travel time for ships traveling between the Atlantic and Pacific oceans. The project was initially controlled by the U.S., but the canal finally transferred into the hands of the Panamanian government in 1999. The canal serves between 13,000 and 14,000 ships annually and was expanded in 2007 to accommodate modern megaships.

The Channel Tunnel, nicknamed the "Chunnel," is an underwater engineering marvel connecting England and France. The tunnel is 31.4 miles long and features the longest undersea portion (23.5 miles) of any tunnel worldwide. Approximately 60,000 passengers make the 35-minute trip through the Chunnel daily, and even the Olympic torch passed through the Chunnel on its way to London in 2012.

Palm Jumeirah is a human-made island off the coast of Dubai. Shaped like a giant palm tree, it was created using 7 million tons of rock and over 4 billion cubic feet of sand. The project took six years to complete and is home to 1,500 beachfront villas. Two more palm islands were initially planned, but only Palm Jumeirah has been completed thus far.

Proposals for a bridge connecting Brooklyn to Manhattan were first made in the early 1800s, but it wasn't until the 1883 opening of the Brooklyn Bridge that the East River received its first fixed crossing. With a main span of nearly 1,600 feet, the structure was the longest suspension bridge in the world when it was completed. In 1964, it was officially designated a National Historic Landmark.

Originally called the Boulder Dam, the Hoover Dam is the highest concrete arch dam in the U.S. It was constructed between 1930 and 1936 and impounds nearby Lake Mead, the largest reservoir by volume in the United States. Not only is the Hoover Dam an engineering marvel, but it is also a tourist destination, welcoming over 7 million visitors annually.