The Canary Islands feature the world's third-largest volcano and the largest natural underwater lava tunnel ... located inside the volcanic tunnel, are natural caves that are open to visitors ...

From a protected cove on Long Island, Dean’s Blue Hole—Earth’s deepest known underwater cave—plunges more than ... at a depth of 130 feet. Here the tunnel narrows and plunges to below ...

The first underwater tunnel was built with a tunnel shield ... 100 The tunnel shield supports the soggy soil so it won't cave in on you as you dig. Here's how it works: The shield, which looks ...

In the south of Denmark a mega project is underway to build a tunnel under the Baltic and providing a link to Germany. It's currently Europe's biggest construction site and the world’s longest ...

Underwater cave diving is a thrilling adventure for those looking to explore beneath the surface. These caves provide an ...

Underwater caves can be dangerous for even the most experienced divers. There is usually no natural light, spaces can be tightly enclosed and twisting tunnels are complex to navigate. But the ...

Sognefjord, the longest and deepest fjord in Norway, has several hidden cave systems just waiting to be explored. Divers can ...

It also features multiple 'jump tunnels' that run off into wider tunnels. Cave Adventures warns the system is a 'low flow cave' that can easily become filled or blocked with silt if divers are not ...

Trains traveling through the tunnel are expected to reach a top speed of 350 kilometers per hour — the highest operating speed for any underwater tunnel in the world — with no reduction in ...

The world's largest shield machine for railway construction has reached the middle point of the tunnel's underwater section on Wednesday, marking a milestone in the construction of the high-speed ...