Why colosseum can last up to now

The Colosseum or Coliseum, also known as the Flavian Amphitheatre, is an oval amphitheatre in the centre of the city of Rome, Italy. Built of travertine, tuff, and brick-faced concrete, it is the largest amphitheatre ever built

Although partially ruined because of damage caused by earthquakes and stone-robbers, the Colosseum is still an iconic symbol of Imperial Rome and is listed as one of the New7Wonders of the World. It is one of Rome's most popular tourist attractions and also has links to the Roman Catholic Church, as each Good Friday the Pope leads a torchlit "Way of the Cross" procession that starts in the area around the Colosseum.

There are some reasons why this architectural wonder has endure over time and they are the material and design used during its construction.

More than 100,000 cubic meters of travertine stone were used for the outer wall of Colosseum. Two main properties of travertine stone are: Impact and Wear Resistant and Resists Heat and Pressure, these properties give the material the durability for centuries.

The Colosseum, stands on a 13 meter thick basis and on a travertine ring, to assure stability and resistance. This engineering design gave the structure some seismic resistance to earthquake.

The other main factor of this building over time is the used of concrete at that time. Romans started making concrete more than 2,000 years ago, but it wasn't quite like today's concrete. They had a different formula, which resulted in a substance that was not as strong as the modern product. Yet structures like the Pantheon and the Colosseum have survived for centuries, often with little to no maintenance.

Roman concrete is considerably weaker than modern concretes. It's approximately ten times weaker. What this material is assumed to have is phenomenal resistance over time. That resistance, or durability against the elements, is due to one of the concrete's key ingredients: volcanic ash. Modern concrete is a mix of a lime-based cement, water, sand and so-called aggregates such as fine gravel. The formula for Roman concrete also starts with limestone: builders burned it to produce quicklime and then added water to create a paste. Next they mixed in volcanic ash-usually three parts volcanic ash to one part lime, according to the writings of Vitruvius, a first-century B. C. architect and engineer. The volcanic ash reacted with the lime paste to create a durable mortar that was combined with fist-size chunks of bricks or volcanic rocks called tuff, and then packed into place to form structures like walls or vaults.

All these combined construction techniques have given the coliseum (80 AD) the endurance over time making it the seventh wonder of the world.