World’s 6 Most Expensive Megaprojects; 2025 Review

Money has enabled humans to design, build, and move things at incredible speeds. If we look back to megaprojects such as the Eiffel Tower, which wowed at the time, they now seem a little futile compared to the skyscrapers and construction creations of today.

If something seems impossible, mankind will likely try and conquer it. We have already done amazing things, such as building a tunnel under the English Channel, and flying to the moon, and here are the top 6 most expensive megaprojects of mankind:

World’s 6 Most Expensive Megaprojects

Here are the world’s 6 most expensive megaprojects for 2025 worth learning about:

1. The Interstate Highway System, $459 Billion

One of the most expensive megaprojects, the Interstate Highway System in America connects more than 47,000 miles and takes almost 35 years to complete.

The project involved creating new routes and converting old ones, to serve as ‘interstates’, and has cost the taxpayer a huge $459 billion.

Work began in 1955 after President Dwight D. Eisenhower proposed the project as being crucial for national defense and to help mobilize infantry in an emergency. Thanks to the project, travel for both citizens and the military has been improved, and there are more accessible routes in case of war.

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2. The International Space Station, $150 Billion

The ISS orbits Earth and enables scientists to conduct experiments in astronomy, biology, and physics. Built-in 1994 on Earth and assembled in space, fourteen countries worked together to complete this project.

The main tools used were Russian rockets and the space shuttle, and the station was not inhabited until two years into construction when the Russian module Zvezda was added containing pressurizing equipment and sleeping quarters.

After 26 years of service, the ISS, one of the most expensive megaprojects is to be crashed into the ocean in 2020.

3. Kashagan Fields, $116 Billion

The largest oil discovery in the past 40 years led to the Kashagan Fields, located in the Caspian Sea, and commercial production began in September 2013.

Part of the construction of one of the most expensive megaprojects includes building man-made islands in a sea frozen for large periods of time. Leaks in pipes and other challenges have caused delays in the construction of the project, and the fields are under high pressure making drilling into them very dangerous.

The operation is expected to start in 2017 and produce over 90,000 barrels of oil per day. Experts estimate the production yield to total as much as 13 billion barrels of retrievable oil.

4. King Abdullah Economic City, $95 Billion

Construction of the Saudi Arabian city is expected to be finished in 2020, yet in 2015, only 15 percent had been completed. Named after the late King Abdullah, the city will be slightly larger than Washington D.C. and will house 2 million residents.

Located over an hour away from Mecca, the city is set to become a new tourist attraction for Saudi Arabia and will boast high-class hotels, luxury villas, prestigious universities, and a massive airport. It will also be home to residential neighborhoods, with a hope of diversifying the region’s economies.

The project is being built by real estate group Emaar Properties, who are known for building Burj Khalifa in Dubai, the world’s tallest building.

5. Dubailand, $76 Billion+

When Dubailand was announced in 2003, it was one of the most ambitious leisure developments ever proposed anywhere in the world. It is not even complete and is already one of the most expensive megaprojects.

The reason behind Dubailand was that some thought Dubai needed a major attraction geared towards families. There are design aspects based on Arabian Folklore and plans for a Disney theme park, an IMAX theatre, and many other attractions.

Construction was halted on this project in 2008, due to a financial crisis, and resumed in 2013; Current estimates predict that Dubailand will open before 2020.

6. California High Speed Rail, $33 billion+

Work on the California High Speed Rail started in 2015, and phase 1 is set to be completed by 2029. It is already way over its original budget and is tipped to reach $98.5 billion.

The first phase is planned to run between Madera and Bakersfield, and was one of President Obama’s first-term pledges, to connect the major US cities by high-speed rail.

The high-speed ‘bullet train’ will stretch between San Francisco and Los Angeles, with rails that can support travel up to 220 mph.

Successful Megaprojects Depend Upon Accurate Cost Estimation.

We used to think a megaproject was large when it exceeded $10 billion. Now it’s common to see megaproject budgets easily exceed $100 billion. Within the next 5 years, due to inflationary pressure, we will likely see the first $1 trillion megaproject.

But it’s important to realize that due to the sheer size and complexity of these construction projects when they go wrong, communities and in some cases national economies, are devastated. Many of these megaprojects, which were developed ostensibly to be eco-friendly, have sparked or further contributed to habitat and wildlife devastation.

In many cases, the primary cause of the problems that cause cost and schedule overruns for megaprojects can be attributed to poor planning specifically, failure to develop an adequate cost estimate for the project. Ultimately, what these cautionary tales illustrate is that failure to adequately plan and/or control risks in construction results in budget and schedule creep that can destroy projects–no matter how large or small.

Conclusion

Throughout history, humans have believed that bigger is better with colossal construction projects. Pyramids, religious monuments, skyscrapers, and other buildings deemed important to the lives of people thousands of years ago and today testify to this belief.

These most expensive megaprojects demonstrate the vision, ingenuity, and drive of humans since they left the caves and began to erect buildings. Mankind has consistently endeavored to push the limits.

As technology, machinery, and construction methods improve, the size and scope of what builders can create expands. However, massive projects must overcome tremendous obstacles, from having to navigate increasingly complex politics and government regulations to overcoming opposition from environmental and social activist groups.

FAQs 

What are the World’s 6 Most Expensive Megaprojects?

• Answer: 1. The Interstate Highway System, $459 billion – 2. The International Space Station, $150 billion – 3. Kashagan Fields, $116 billion – 4. King Abdullah Economic City, $95 billion – 5. Dubailand, $76 billion+ – 6. California High Speed Rail, $33 billion+

What is the most expensive Megaproject ever undertaken?

• Answer: The Interstate Highway System in the United States is the costliest mega project in history, with a staggering price tag of $459 billion. It spans more than 47,000 miles and took nearly 35 years to complete, revolutionizing travel and enhancing national defense.

Why is the International Space Station (ISS) considered a landmark mega project?

• Answer: The ISS is an extraordinary $150 billion endeavor, constructed through the collaboration of 14 countries. Built-in 1994 and assembled in orbit, it allows scientists to conduct groundbreaking experiments in areas like astronomy and physics, making it a marvel of international teamwork and engineering.

What risks do mega projects face during construction?

• Answer: Mega projects often encounter budget and schedule overruns due to inadequate planning and cost estimation. Poor risk management can lead to delays, habitat destruction, or economic setbacks, highlighting the importance of thorough preparation and control in such large-scale developments.

Resources:

Forbes | Construction Briefing | Integra Recruitment | Concrete Construction | 1build | Archdaily

For all the pictures: Archdaily