Things you never knew about the Seven Wonders of the World

The Great Wall of China snakes along the nation's ancient northern border, and protected the southern states from invasion, right up until the Manchu Conquest of the 17th Century. There are many myths about the Great Wall (you can't see it from space) but what are the facts?

The Great Wall isn't really one wall; it's a series of walls of different ages and different styles. This section is the most famous and also the most recent. It was built only around 450 years ago. The oldest parts are just earthen mounds and date back 2000 years.

The city of Petra in modern-day Jordan is a true wonder to behold. Many of the buildings of this 2300 year old Nabatean city were carved directly into solid rock. Their striking appearance has led to this abandoned city becoming a major tourist destination.

Structures like 'The Treasury' and 'The Palace of Pharaoh's Daughter' decorate tourists' postcards, but did you know that nearly four fifths of the ancient city remains underground and unexplored? There may be many more unbelievable buildings waiting to be discovered.

The Taj Mahal, found in Agra, India, was the work of the Mughal emperor Shah Jahan, who built this perfectly white, perfectly symmetrical marble tomb as a monument to his favourite wife, Mumtaz Mahal. In total, it took 20,000 workers and 1,000 elephants 16 years to build.

But did you know that the sarcophagi inside are actually empty? The Islamic prohibition of wealthy, ornate tombs meant that Shah Jahan and Mumtaz Mahal were buried in a smaller, simple tomb one level below ground…

… This room is rarely opened, because breath of visitors would damage the white marble walls.

Christ the Redeemer stands on the peak of the Corcovado mountain, towering above the Brazilian city of Rio de Janeiro. Completed in 1933, the statue is an emblem of Christian faith and national pride. At 30m tall and with arms stretching 28m wide, it's hard to miss.

But did you know that while the statue stands in Brazil, Christ's face was actually made in France? It was carved from solid soapstone by the Romanian sculptor Gheorghe Leonida, then living in Paris. In total, it took Leonida five years to complete the piece!

Machu Picchu clings to the ridgeline of the Eastern Cordillera of southern Peru. This stone citadel was constructed as an estate for the Inca emperor Pachacuti around 1450 and abandoned around the time of the Spanish conquest. It was only discovered by Europeans in 1911!

In the time of the Inca, this 'lost city' was regarded as the centre of the world. The Intihuatana was a ritual stone platform at Machu Picchu that may have been used as a sundial or altar. Here, essential rituals would have been carried out to ensure the cycle of the sun.

The Mayan city of Chichén Itzá in modern-day Mexico was perhaps the largest urban area in the pre-Colombian Americas. Occupied between 600-1100CE, the city supported a complex and diverse society, and became a major economic and political centre of the region.

You may know about the numerous stepped pyramid temples and the famous Great Ball Court (seen here), but did you know that the city also contained a bath house with a steam sauna, paved causeways known as sacbeob, and a tzompantli, or 'skull rack'.

In ancient Rome, there were few better ways to spend an afternoon than taking in a game at the Colosseum, then known as the Flavian Amphitheatre. Built in 72CE, this building hosted gladiatorial matches, musical events, executions, and even a small-scale sea battle.

But did you know that besides being a monument to gore and glory, the Colosseum is also home to many plants and animals? In 1643, the herbalist Domenico Panaroli surveyed all the plants growing on the ruins. Since then, 684 different species have been identified.