10. The Coliseum

The Coliseum was probably built, as many great Roman buildings were, in celebration of a military triumph. It is estimated that the Coliseum held between 50,000 and 80,000 spectators, putting it on par with many modern sports stadiums, but it was an engineering marvel. Over 157-feet tall and 620-feet long, the Coliseum was an enormous undertaking, even for the Romans and their advanced engineering abilities. They introduced arches and vaults to give the building extra strength, and below the arena was a complex system of tunnels, elevators and even hydraulic mechanisms. The Roman Empire embarked upon this longest construction project to create a physical symbol of the glory of Rome.
AD 70 - AD 80 Total time: 10 Years
9. Parthenon

The Parthenon was built in the 5th century B.C. and sits on the Acropolis hill above Athens. This longest construction project was built as a temple to the Goddess Athena. Greek architecture was hugely influential in Roman building and the neoclassical architecture of later centuries. Some studies have suggested that the Parthenon was built to mirror the Golden Ratio, a mathematical constant which is believed to be the ideal of aesthetic beauty. This level of sophistication was unparalleled in the architecture of this era. It was regarded as the finest Doric temple in ancient Greece, and belongs on our list of top 10 longest construction projects because it was built with such detail and accuracy at a time when some societies still lived in caves.
447 BC - 430 BC Total time: 17 years
8. The Great Pyramid of Giza

These ancient Egyptian monuments are among the most famous buildings in the world. The largest on this site was built for the Pharaoh Khufu around 2,550 B.C., taking approximately 20 years to complete, and was the tallest man-made structure in the world until the building of the Eiffel Tower. The Great Pyramid represented the apogee of Egyptian building prowess, and were the culmination of many previous pyramid designs. An astonishing feat of geometric accuracy, this longest construction project aligns perfectly with the stars, and they are accurate to within millimeters. Debate still rages over how they were built, as the Egyptians lacked tools such as pulleys to help move the immense 2.5-ton stones.
2580 BC - 2560 BC Total time: 20 years
7. Sacsayhuamán

Built overlooking the capitol of the Incan Empire in Cuzco, Peru, Sacsayhuamán is a glorious example of the imagination of South American civilizations. The walled complex was designed to represent the head of a puma, with the rest of the city designed as its body. It is all the more remarkable because they used a mortarless construction method, where the stones were carved to interlock so tightly that it was impossible to fit even a piece of paper between them. How the stones were hewed, moved and placed is still uncertain, but some believe there was a workforce of some 30,000 men working to build this longest construction project.
AD 1445 - AD 1508 Total time: 63 years
6. York Minster Cathedral

There are many medieval cathedrals that compete for a place on our list, but York Minster is a worthy addition to the top 10 longest construction projects. Started by the Archbishop Walter de Gray in 1220, construction of this massive project was not completed until 1472. It contains the largest example of medieval stained glass in the world, and is some 520-feet long. Its three towers are each almost 200-feet tall. York Minster was built using purely medieval techniques and equipment, and still took over two centuries of continuous construction to complete. It is a wonderful example of the grand designs and technical skill of medieval craftsmen.
AD 1220 - AD 1472 Total time: 252 years
5. Chichen Itza

Located on the Yucatán Peninsula of Mexico, Chichen Itza is one of the most well known Mayan settlements. Probably started around A.D. 600, the complex covers an area of six square miles. Chichen Itza’s Great Pyramid was designed to enhance the sound of a speaker at the top, and the vernal equinox casts a shadow of a writhing serpent down the steps, making it a breathtaking example of mathematical precision and artistic imagination. South American civilizations lacked the domesticated livestock that European and Asian societies used to haul heavy stones, and they never used the wheel for industrial purposes, making such a sophisticated construction project even more remarkable.
AD 600 - AD 1.000 Total time: 400 years
4. Angkor Wat

Built in the mid-12th century by the ruler of the Khmer Empire in Cambodia, the central temple was part of a much larger community of buildings that together made up one of the largest preindustrial cities in the world. The 2.2 mile-long outer wall encloses a space of 203 acres, including a moat. The temple itself is part of a series of more than 100 and is built on three rectangular galleries, each one higher than the previous, and is a tribute to the Hindu God Vishnu. Despite being lost to the jungle for many years, this longest construction project remains the finest example of Khmer architecture in the world.
AD 802 - AD 1220 Total time: 418 years
3. Petra

Few construction projects have the dramatic appearance of Petra, a citadel in the middle of the desert in Jordan, carved straight into the rock. The famous façade is nearly 100-feet wide and 141-feet tall, built by the Nabataeans in the A.D. 1 who had first settled there around 600 B.C. At its peak, Petra may have been home to some 20,000 people, and was a key center of the trade routes of the Near East. Lacking modern tools to cut and shape the rock meant this longest construction project was a far more challenging undertaking, especially given that the Nabataeans were originally a nomadic society.
600 BC - AD 250 Total time: 850 years
2. Stonehenge

Despite being about 5,000 years old, no one is certain why Stonehenge was built. Clearly, it is one of the most incredible construction projects ever conceived. Each stone weighs over four tons and was dragged over 240 miles from southern Wales to its final resting place in Wiltshire, England. It is believed to have taken over 1,500 years to be completed, and to have required around 30 million man hours. Apart from the sheer effort needed to complete this longest construction project, it was built with remarkable precision, aligned perfectly with solar and lunar movements with particular emphasis on the summer and winter solstices. It is a truly remarkable feat for a Neolithic society.
3100 BC - 1500 BC Total time: 1600 years
1. The Great Wall

Started over 2,000 years ago, and still being constructed during the 16th century A.D., the Great Wall was actually a series of walls constructed by different dynasties over the centuries. Stretching over 4,160 miles at its peak, the wall was guarded by over one million men, protecting the northern border of China against fearsome nomadic raiders. It is estimated that between two and three million men died during its construction. The Great Wall was as much a symbol of imperial power as it was an effective military tool, and is unrivaled to this day as the world’s longest construction project.
400 BC - 1600 AD Total time: 2000 years
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