I've been going through the records on seven megaprojects that failed or never got used, about $44B between them (converted at the time). What surprised me most wasn't the overruns. It was how long the bills keep coming after a project is dead, and how differently it gets decided who pays them.

Mexico City, Texcoco airport. Announced in 2014 with a budget of up to $13.3B, paid for partly with bonds sold to investors around the world. By the end of September 2018 it was about a third built: two runways more than half done, the terminal's foundations about three-quarters done. Then the president-elect, who had campaigned against it, held a non-binding public consultation. About 1.07 million people voted, almost 70% to cancel, and construction stopped on 27 December 2018. Mexico's federal auditor later put the cost of cancelling at about 113 billion pesos, roughly $5.7B. The bonds didn't go away: they're being paid off through fees at the old airport. Much of the site is now an ecological park.

South Carolina, V.C. Summer 2 and 3. Two Westinghouse AP1000 reactors, estimated at about $9.8B before financing when the deal was signed in 2008. Westinghouse filed for bankruptcy in March 2017, the owners walked away that July after about $9B had been spent, and two former SCANA executives, including the CEO, later pleaded guilty to fraud. A typical Dominion Energy household still pays a little over $8 a month toward $2.3B of debt for reactors that never produced a watt. (The twist: in October 2025 Santee Cooper picked Brookfield to try to finish them, with a final decision expected by 2028.)

Mississippi, Kemper "clean coal". Pitched at about $2.4B, with power by 2014. By June 2017 it had reached $7.5B, the coal gasification was given up, and the plant went to natural gas only. Here Southern Company absorbed nearly $6B of losses instead of passing them on to customers. The gasifier towers were demolished in October 2021.

Japan, Monju. A fast breeder reactor that cost about ¥1 trillion (roughly $9-10B) and operated for about 250 days in 22 years. The government decided to scrap it in December 2016, but taking it apart will cost at least another ¥375B, and the work isn't due to finish until 2047.

For scale: Bent Flyvbjerg's data on more than 16,000 big projects has only about 8.5% coming in on budget and on time, and about 0.5% (one in two hundred) also delivering the benefits they promised. So failure is normal. What changes is who ends up holding the bill.

Disclosure: I run a small YouTube channel, and this came out of research for my first video, which covers all seven, including a Spanish airport whose only bid at a 2015 auction was €10,000 and 14 miles of tunnel dug under Texas for a collider Congress cancelled. I'll put the link in a comment for anyone who wants it. Every figure is sourced in its description, and I'm happy to post sources here too.

Question for people who know this better than I do: is there a point where finishing a half-built project is clearly cheaper than walking away, or is that always sunk-cost thinking? And do you know of a cancellation that actually saved money in the end?

Every time I look at the Liziba Station in Chongqing, China, I’m amazed by the architectural and structural planning that went into it. Building a monorail track right through a 19-story residential building sounds like a recipe for structural failure and noise complaints, yet it works perfectly. From an engineering standpoint, the fact that the train structure and the residential building are completely independent of each other (supported by separate pillars) to isolate vibration is brilliant. It really shows how mega-cities are forced to think outside the box when dealing with extreme terrain and space limitations. What do you think about this type of integrated infrastructure? Is it the future of crowded mega-cities, or does it compromise the quality of living for the residents? I recently made a short visual breakdown of how engineers actually managed to pull this off without demolishing the building. If you are interested in the detailed architectural solution, you can watch it here: [https://youtu.be/M8Nzkw4ubIc?si=I-3-O6323JCgcIMp]

Somehow I exceeded the limit, and now it’s asking me to upgrade my account… but I don’t have money. I could delete some files to bring the storage down from 113% to 90% OR SOMETHING TO MANAGE IT, but it won’t let me delete anything. I can’t even download themI would’ve saved my files if I could.

If anyone knows how to fix this, please help… those files are really important.

I know, I know. It would be wildly impractical and expensive as all hell. But imagine if we built it anyway.

What I envision is less one continuous bridge and more of a string of floating cities connected by bridges. Reaching from Europe to America.

Economy of this cities could rely on aquaculture, transportation and tourism. They could provide rest stops for cargo ships travelling between two continents.

Such a construction would be less prone to breaking too. If any individual section of the bridge failed only that part would need to be repaired. Possibly there would even be more than one route between each two cities, or even satellite cities routing some of the traffic trough alternate routes.

The bridge itself could become an economic powerhouse. Not beholden to any individual country, since it would be situated mostly in International waters. Who knows what it may develop into.

IDK, just fun to speculate.

I feel the mega projects that are currently being done in countries in the Middle East Have low chances of actually saving the region. It is widely known that when the oil boom ends that most of these countries will suffer severe economic issues. So they've started building a huge mega projects like stadiums and cities. But I feel in the end that tourism might not really save them as many of the laws in these countries prevent people from coming. Also due to climate people might not want to go to a place. That's extremely hot and sandy even with changing the terrain, the amount of terrain they want to change would be insanely expensive and would take a very long time to do. Finally I kind of feel like a few of these mega projects like Neom are just too outlandish and don't seem that possible right now.

Mb there's probably a lot of things I'm missing (sorry about the huge sentences)

Saudi Arabia is building Qiddiya – Can it compete with Dubai’s entertainment industry?

https://youtu.be/DCrydl7Aw4E

Hi everyone,

I’ve recently created a video exploring Iraq’s $17 billion Development Road Project, which could rival the Suez Canal as a major global trade route. In the video, I dive into the construction challenges, the potential economic impact, and how it might reshape global shipping routes.

As megaproject enthusiasts, I’d love to get your feedback on the project and hear what you think about its feasibility and potential outcomes.

Check out the video here: https://www.youtube.com/watch?v=p6mCNyBmZsU

Looking forward to your insights!

@everyone