The idea of a bridge (or tunnel) across the Cook Strait – finally linking the North and South Islands and doing ahead with the need for long (and frequently cancelled) ferry rides – is something that many people have speculated about, but is again in the news.

While its feasibility is still being debated, we take a look at a few other proposed projects linking things – as well as a few that have already been build that were previously thought to be impossible.

Bering Strait Crossing

The Bering Strait is “only” about 82 kilometres at its narrowest point between Russia and the US state of Alaska – and the idea of a bridge or tunnel connecting the two large nations has been floated since at least the 19th century. With a group of islands roughly in the middle of the strait, a bridge or tunnel would not need to be as long as some might think. However, the extreme cold, depth of the water and incredibly strong currents of the Bering Strait (which also connects the Pacific Ocean with the Arctic Ocean) pose major engineering challenges, as would the extreme cost (estimated to be tens of billions, if not hundreds of billions, US dollars) and need to develop extensive infrastructure (such as roads and railways) on either side of the crossing (the areas around the Bering Strait in both the US and Russia are – outside of Antarctica – among the most undeveloped places on Earth). Then there’s also the fact construction would take many years, and that US-Russian relations are at their worst since the Cold War (which prevented any serious work previously).

Still, if it is one day built… how EPIC would it be to literally drive from London to Miami?!

A bridge between India and Sri Lanka

Sri Lanka is an island… but is only separated from the Indian subcontinent by a 50-kilometre series of shoals known as the Ram Setu Bridge (or Adam’s Bridge). While not technically a bridge, some people believe the rocks are actually part of a human-made bridge that was built by Lord Rama – as per Hindu legend – before it was destroyed. According to the Hindu epic Ramayana, Rama and his army of monkeys built the bridge and crossed over to Sri Lanka to rescue Rama’s consort, Sita, from the demon king Ravana.

Origins aside, the idea of a man-made bridge linking India and Sri Lanka has been proposed before, but has been replaced by the Sethusamudram Shipping Canal Project, which would see the seafloor dredged so that large shipping vessels could safely sail through the area.

Are the ancient Hindu myths of a land bridge connecting India and Sri Lanka true? Scientific analysis suggests they are. #WhatonEarth pic.twitter.com/EKcoGzlEET

— Science Channel (@ScienceChannel) December 11, 2017

Gotthard Base Tunnel

The 57-kilometre-long Gotthard Base Tunnel is the world’s longest and deepest traffic tunnel – as well as the first flat, low-level route through the Alps. Construction – once considered all but impossible – took about 17 years, beginning in late 1999 and culminating with the tunnel opening in 2016. It cost more than 9.5 billion Swiss francs (more than NZ$14 billion) to build.

Channel Tunnel

Also known as the Chunnel (or Le tunnel sous la Manche in French – sounds more romantic, eh?), this tunnel linking the UK and France by travelling beneath the English Channel was considered an engineering marvel when it opened in 1994 – and still is. Today, more than 20 million people pass through the tunnel every year.

Irish Sea Tunnel

Another proposed undersea tunnel, this one linking the island of Ireland with the UK. While the shortest distance is about 19 kilometres between Northern Ireland and Scotland, construction – if it went ahead – would still likely cost tens of billions of pounds.

Japan-Korea Undersea Tunnel

Japan and South Korea are about 128 kilometres apart at their shortest distance – and the idea of a tunnel connecting the two nations has been floated since at least 1917, when Korea was ruled by Japan. Today, former South Korean president Lee Myung-bak is a supporter of the project. But it would still costs billions – and many people in both nations are opposed to the idea of being linked partially due to a long and bloody history of distrust between them.

Evergreen Point Floating Bridge

Officially the Governor Albert D. Rosellini Bridge (and commonly called the SR 520 Bridge, or 520 Bridge), this was a floating bridge in the US state of Washington that carried State Route 520 across Lake Washington. Opened in 1963, it was replaced by a newer floating bridge in 2016. When it opened, its 2,310-metre-long floating section made it the longest floating bridge in the world.

Overseas Highway

Stretching about 182 kilometres, this road network connects the Florida Keys with the mainland United States. Much of it is built over the Atlantic Ocean. It’s actually a lot older than a lot of people might think, too, dating back to 1928 (and even then was built largely atop the so-called Overseas Railroad, which opened in 1905).

Øresund Bridge

A combined railway and motorway bridge across the Øresund strait between Sweden and Denmark, this bridge runs nearly eight kilometres from the Swedish coast to the artificial island of Peberholm. Designed by the Danish engineering firm COWI and opened in 2000, the bridge is one of the most important connections between Sweden, Norway and Finland with Western Europe.

Norwegian submerged floating bridges

It can take about 21 hours to drive from the southern Norwegian port of Kristiansand to Trondheim, due to the fact you have to drive around numerous gorgeous (but difficult to traverse) fjords. It’s difficult to build bridges above many of the fjords, too, as they are incredibly deep (among other challenges). Now, the Norwegian government is pumping tens of billions into “submerged floating bridges” to solve this problem and cut the travel time in half. In short, motorists will be able to drive through tunnels that float semi-suspended in the water – think giant pipes connecting things. The goal is to have the submerged floating bridges – an idea which has never been tried on a large scale before – up and running by 2035. We can’t wait.