Top 10 Greatest Megaprojects in Human History

Do you know what humanity's most insane ideas are? Is it building a 170-kilometer-long linear city in the desert? Or carving a continental-scale artificial river under the Sahara? Or perhaps assembling a permanent space metropolis in low-Earth orbit? These may sound like science fiction, but they have already become reality. Let's take a look at the top 10 craziest megaprojects in human history. Number 10. China's Three Gorges Dam. 2,400 meters long, 185 meters high, maximum reservoir capacity of 39.3 billion cubic meters, more than 27 million cubic meters of concrete. These numbers alone surpass most hydraulic projects. The Three Gorges Dam is the largest hydroelectric complex on Earth, bar none. It is not just a power plant, but a national-scale supersystem combining flood control, power generation, navigation, water diversion, and ecological regulation. The dam spans the upper and middle reaches of the Yangtze River, taming China's most turbulent water system. With an installed capacity of 22.5 million kilowatts, 32 turbine generators produce over 100 billion kWh annually, once holding the world record for single-station hydroelectric output. But the true complexity is not power generation, it's water regulation. The upper Yangtze is one of China's most flood-prone regions. By adjusting reservoir levels, the dam protects downstream cities from flooding. Every flood season, the entire system goes into wartime mode, with water-level control requiring centimeter-level precision as millions of lives are at stake. Construction began in 1994 and was completed in 2009, taking 15 years with an investment of about $30 billion. It involved resettling millions of people, rebuilding shipping systems, and implementing massive geological reinforcements. The dam includes a five-step, two-way shiplock, with a vertical drop of nearly 113 meters. To solve ship passage, a 3,000-ton shiplift was also built, allowing vessels to ride an elevator across the dam. Number 9. Kazakhstan's Kashagan Oil Field Located in the northern Caspian Sea, Kashagan is one of the largest oil discoveries of the 21st century, with proven reserves exceeding 30 billion barrels. But what makes it world-class is not its reserves, but its extreme development difficulty. For more than five months each year, the sea is frozen, with temperatures dropping to 40 degree. The oil field lies in shallow waters less than 4 meters deep, making conventional drilling platforms impossible. Engineers had to build artificial islands as drilling and production bases, a rarity in global oil field development. The geology is equally extreme. Reservoirs buried more than 4,000 meters deep, with ultra-high pressures and high concentrations of toxic hydrogen sulfide. Equipment had to be made of high-grade anti-corrosion alloys, with constant gas monitoring and safety systems. With investment exceeding 50 billion dollars, Kashagan is recognized as one of the most expensive energy projects ever. The oil is piped to the Atirau refinery and into cross-border export routes, serving as a pillar of Kazakhstan's national energy strategy. Number 8. Saudi Arabia's Grand Mosque in Mecca The Grand Mosque of Mecca in western Saudi Arabia is the world's largest and most complex religious building complex and the most important pilgrimage site in Islam. Its core is the Kaaba, the direction of daily prayer for all Muslims. The complex covers about 400,000 square meters. The main prayer area can hold 1.5 to 2 million people at once. During peak pilgrimage, the city of Mecca accommodates over 3 million. It consists of multiple levels, the central courtyard, circular walkways, elevated platforms, underground passages, annexes, plazas, medical stations and transit nodes, forming a high-density human flow management system. Since the mid-20th century, the mosque has undergone continuous expansions. After 2008, major upgrades increased capacity from about 2 million to more than 4 million, adding over 300,000 square meters of new construction. Nearby stands the Abraj al-Bayt Tower Complex, its central clock tower rising 601 meters, the world's second tallest building. The Grand Mosque is not a single building, but a vast integrated system serving prayer, walking, gathering, safety, accommodation and logistics. Its expansion and operation remain a dynamic, ongoing national project. Number 7. China's South-to-North Water Diversion Project This mega project addresses northern China's chronic water shortages. It has three routes, eastern, central and western. With a planned capacity exceeding 44 billion cubic meters, making it the largest water transfer project in the world. The key is the central route, starting from the Danjiangkou Reservoir in Hubei, running 1,532 km north through 13 major cities to Beijing and Tianjin. Its uniqueness, it relies entirely on gravity flow. No pumps, just carefully calculated gradients with tolerances of only a few centimeters. To cross the Yellow River, engineers built a 70 meter deep inverted siphon tunnel, allowing giant pipelines to pass under the river. The system includes regulating reservoirs, distribution hubs, tunnels and monitoring stations. The central route now supplies over 70% of Beijing's water, serving more than 100 million people across northern China. The eastern route modifies the Grand Canal, requiring 23 pumping stations to lift water through Jiangsu, Shandong and Anhui. The western route is still in planning. So far, investment has exceeded 70 billion dollars, involving massive resettlement and ecological measures, relocating more than 350,000 people. This project reshaped water use for dozens of northern cities, showing that water need not be limited by geography. Number 6. India's Statue of Unity The tallest statue in the world, 182 meters high, over 240 men altars, including base, twice the height of the Statue of Liberty and three times Rio's Christ the Redeemer. Located in Gujarat state, on the banks of the Narmada River, it honors independence leader Sardar Vallabhbhai Patel. Completed in 2018, it cost about 430 million dollars. Its structure, concrete core plus steel framework plus copper cladding. It used 21,000 tons of steel, 70,000 tons of cement and 1,800 copper panels, cast in China and assembled on site. Four core columns provide stability, designed to withstand 60 Menares winds and magnitude 6.5 earthquakes with a lifespan of over 100 years. Inside are elevators, stairs and ventilation. Visitors reach a viewing platform at 135 meters in the statue's chest. The base contains a museum and digital exhibits on Patel and India's independence. Built in just 42 months, with over 3,000 workers and engineers at peak, it fused sculpture, structural engineering, high-rise construction and precision installation. A record-breaking architectural feat. Number 5. Japan's Kansai International Airport. This is an airport that has been sinking since day one. It was built entirely offshore, on an artificial island in Osaka Bay, 5 kilometers from shore. Covering more than 10 square kilometers, it required 230 million cubic meters of fill, essentially leveling mountains and dumping them into the sea. Construction began in 1987, taking 8 years just to stabilize the soft seabed, 60 Menares thick clay layers. To slow settlement, engineers drove 90,000 sand columns and reinforced slopes. Designed by Renzo Piano, the airport has two runways, 3,500 meters and 4,000 diameters, and a 1.7 kilometer terminal, the world's longest single airport building. It is linked to Osaka by a 3.75 kilometer bridge, carrying both highway and rail, with underground rail and subway at the terminal. Phase 1 cost 20 billion dollars, taking nearly 10 years to build. Despite constant settlement, the airport still operates normally. It is a project forever battling geology, the sea and gravity. An airport that cannot stop sinking, only endure. Number 4. Libya's great man-made river. Mention the Sahara, and people think of drought. Yet under its southern edge, Libya built a system supplying 6.5 million cubic meters of water daily to coastal cities. The great man-made river is not a river, but a 4,000 kilometer underground pipeline network, pumping fossil water from deep aquifers. Started in 1984, built in 5 phases by state-owned companies, it taps 4 major aquifers holding an estimated 30 trillion cubic meters. Over 1,300 wells, each over 300 meters deep, feed pumping stations, reservoirs and control towers. Water flows through 4 meter diameter pipes, each 80 tons, prefabricated in factories and laid in trenches up to 7 meters deep. It supplies over 70% of Libyans with water for cities and farms. This hidden pipeline web beneath the desert is Libya's most vital infrastructure. Number 3. Saudi Arabia's Jubail Industrial City. Before the 1970s, this was a fishing village on the Persian Gulf. Then Bechtel and the Saudi government began building a city for industry. Phase Y made up 7% of national GDP. By 2005, the kingdom launched Jubail 2, doubling its scale. Covering 687 square miles, the 22-year plan was estimated at $80 billion for infrastructure alone. Not just an industrial park, a city engineered for production. Housing for 120,000 residents, a university for 18,000 students, ports, utilities, cooling water networks, gas pipelines, waste treatment, everything built for industry. At peak, 20,000 workers per month served petrochemical, refining, and gas facilities operated with Aramco, Sabic, Total, and others. Jubail is not a traditional city, but an industrial ecosystem, reverse-designed for factories first, people second. Number 2. Saudi Arabia's Neom Project. In the empty northwest desert near the Red Sea, Saudi Arabia plans Neom, 26,000 square kilometers, the size of Albania. It consists of three audacious parts. The Line, a 170-kilometer-long, 200-minutes-wide, 500-meter-tall linear city housing 9 million people. No roads or cars, just a high-speed rail crossing end-to-end in 20 minutes. Oxygen, a floating industrial port city over 200 kilometers, designed for automated zero-carbon manufacturing. Trojena, a mountain ski resort at 2,500-meter altitude with slopes, lakes, and hotels, the Middle East's first year-round ski city. Launched in 2017 under the PIF Sovereign Wealth Fund, it is planned to be completed by 2045, with investment exceeding $500 billion. Neom is not retrofitting an old city, it is building the future directly on desert sand. Number 1. The International Space Station, ISS. Orbiting 400 kilometers above Earth, this is humanity's greatest space engineering feat. Built by 16 countries over 15 years, costing over $100 billion, it circles Earth 16 times a day, every 90 minutes bringing sunrise and sunset. Built piece by piece since 1998, with dozens of launches, dockings, and spacewalks. Weighing over 420 tons, solar panels span a football field, housing six astronauts long-term. It generates power, recycles water, supplies air, and runs life support, though regular resupply missions remain essential. Since November 2000, it has never been unoccupied. Over 280 astronauts from 20-plus countries have conducted 3,000 experiments. Managed jointly by NASA, Roscosmos, ESA, JAXA, and CSA, with control centers around the world, the ISS remains the most complex, expensive, and long-running international engineering collaboration ever. From desert cities to orbital laboratories, from buried rivers to industrial ecosystems, these megaprojects prove one thing, humanity never stops pushing its boundaries. Perhaps the next megaproject is already on the drawing board. Thanks for watching, share your thoughts, subscribe, and see you next time.