London's subway system, known as "the Tube," is adding nine new stations and 26 miles of tunnels. It's the biggest engineering project in Europe and needs massive tunnel boring machines to get the job done.

London's Tower Bridge is unique because it's made of metal instead of stone. Also, see how the UK's first cable car is being built to cross the river Thames.

The Tokyo Skytree is the tallest tower in the world. Take a look under the steel to see what keeps the tower standing tall and strong.

New Orleans lies up to 10 feet below sea level and is surrounded by water. When a hurricane hits, the city is threatened from all sides

Learn how Roman engineers kept water flowing for miles around the expansive metropolis.

Hurricane Katrina devastated much of New Orleans in 2005. Many people thought the city's Superdome was indestructible - but it wasn't. Now engineers take innovative steps to stop the next big storm from wreaking havoc.

Romans amassed so much rubbish, there is an entire hill made from ancient garbage and broken shards of terracotta shipping containers.

The Eiffel Tower was the tallest structure in the world for more than 40 years. Today, it's the most iconic landmark in Paris. See what lies hidden from the naked eye.

Below the streets of Toronto is a marvel of engineering called PATH - a network of underground shopping malls, subway stations and pathways that provide shelter from harsh winter weather.

Paris has the second busiest Metro hub in Europe but cracks in the rocks could be a serious safety problem. Travel beneath Paris to explore a hidden world underneath the surface.

Creating and preserving ice strong enough to withstand a professional ice hockey game is a science and an art. See how the Air Canada Center was constructed and how it's maintained for perfect hockey games.

Still standing firm more than 500 years after being built, Machu Picchu continues to provide engineering lessons to those studying the ancient site. How did the Inca build such a site?

The roads to Machu Picchu aren't built for wheeled vehicles. Instead, they're carefully constructed so that humans and animals can traverse steep cliffs on staircases built into the mountainside.

More than 1000 tremors rock Los Angeles every year. Many are small but some are devastating. Scientists from NASA's Jet Propulsion laboratory have innovative technology to discover which buildings are most at risk.

In Los Angeles, there?s always the risk of the next big quake. Engineers must quake-proof buildings to keep city residents safe; these innovative techniques allow the entire structure to move when the ground beneath shakes.

Each sword maker has his own formula, creating a extremely hard blade with willow like flexibility.