It is increasingly common to find London properties that have more subterranean interior space than above-ground square footage, a byproduct of the wealthy desiring to build additions without tripping over surface-oriented building codes. New legislation in some boroughs of the city aims to cut down on permits issue to such underground expansions and could provide guidance for other cities dealing with similar issues around the world.

While not entirely unique to England, the phenomena has reached a critical point in the region. In Greater London, anecdotes around these mega-basements abound, including stories of the compromising neighboring houses by undermining their structural integrity. As Curbed reports: “In a famous case from 2012, excavation work under the mansion of a Goldmann Sachs director resulted in his neighbor getting trapped inside her home, unable to open her front door since it had shifted so much.”

Indeed, the billionaires building these projects do a lot of strange things to maintain their bottom line while maximizing their additions, including leaving diggers worth thousands of dollars each (millions in aggregate) buried in unmarked and self-dug graves simply because the cost of excavating exceeds that of retrieving them. Like other facets of this phenomena, the lack of visibility relating to such practices has helped keep them hidden from public scrutiny.

Over the last decade, the demand for permits to extend below ground has skyrocketed, increasing by over tenfold. In response to the growing concern over these practices, Chelsea and other boroughs are considering measures including: restricting below-ground extensions to a single story, reducing the distance they can expand beyond the building footprint and capping the total subterranean square footage by project (diagrams via TheDailyMail and TheGuardian).

Finally, any discussion of tunnels and London would be remiss not to mention the famous case of the Mole Man, which helped bring many of these other oddities to light. Without permits or permission of any time, this now-infamous Hackney resident began to burrow beneath his house. William Lyttle ultimately tunneled outward in various directions and well beyond his own property line and underneath adjacent streets and homes. For the safety of all involved, the building has been condemned though there are potential plans in place to turn it into artist housing.

Designed to break records held by the Large Hadron Collider at CERN, the Superconducting Super Collider built (and abandoned) in Texas features fourteen miles of unseen and unused underground tunnels.

Construction on what was to be the largest particle accelerator in the world started in the early 1980s but funding cuts in the early 1990s caused the entire project to be shut down. By that time, billions of dollars were already spent and the expected tag had tripled from 4 to 12 billion, 17 shafts were dug and 14 miles of tunnel excavated (out of a total of 51 planned).

Located on a site near Waxahachie, Texas (south of Dallas, shown on a map below) without existing tunnels (which helped in the building of the LHC), removing millions of tons of soil proved to be a budget-breaking expense for the SSC. The complex has since gained the apt nickname ‘Desertron’ for obvious reasons.

Except for underground generators, most of the major machinery was removed from the site before it was deed to the local county, which in turn sold it to a private corporation planning to turn it into a data center. With an independent power grid and dedicated fiber optic line it seemed like a good fit, but when its would-be developer died in an accident the plans were scrapped. Since then it has remained empty, but has again been purchased, this time by a chemical company.

Many factors have been cited as contributors to its abandonment, including the end of the Cold War with Russia and the comparable amounts being budgeted for the United States’ contribution to the International Space Station – at the time, it seemed to many to that spending as much on the SSC as the ISS would be folly (images via Jim Merithew, AmusingPlanet, Wired and Wikipedia).