Known as Crossrail during its planning and construction stages, the Elizabeth Line crossing central London and out to the suburbs is undoubtedly an iconic tunnel project. The history dates back more than 50 years, though construction only started in 2009, requiring a total of 26 miles of tunnel excavation and station construction below many of the most densely populated neighborhoods in the world.

Tunnelling finished in 2015, though the final completion date for the entire system faced numerous delays until the line opened in May 2022, timed to coincide with the Queen’s Platinum Jubilee. The total cost is the steepest on this list at $25 billion.

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20 iconic tunnels and the staggering price tags they carried