Man-made Structures.

The largest manmade structure in the world is the Great Wall of China.

It is a series of fortifications made of stone, brick, tamped earth, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic tribes of the Eurasian Steppe.

With a total length of over 13,000 miles, the Great Wall is a remarkable feat of human engineering and a testament to the determination and resourcefulness of the Chinese people.

As of my knowledge cutoff in 2021, the tallest manmade structure in the world is the Burj Khalifa in Dubai, United Arab Emirates.

The Burj Khalifa stands at an impressive height of 828 meters (2,722 feet) tall and has 163 floors. It was completed in 2010 and serves as a mixed-purpose building, including residential, commercial, and office space. 

The Burj Khalifa has set numerous records, including being the tallest freestanding structure in the world, the tallest skyscraper, and having the highest occupied floor.

The world's oldest manmade structure is a matter of debate among historians and archaeologists, as it can be challenging to accurately determine the age of ancient structures. 

However, some structures that are considered to be among the oldest include:

·         Göbekli Tepe: located in modern-day Turkey, Göbekli Tepe is estimated to be about 11,000 years old and is considered to be one of the earliest known temple structures in the world.

·         Megalithic Temples of Malta: These temple complexes, which date back to around 3600 BC, are considered to be among the oldest freestanding structures in the world.

·         Stonehenge: located in England, Stonehenge is estimated to be around 5,000 years old and is one of the world's most famous prehistoric structures.

·         The Great Pyramids of Giza: Located in Egypt, the pyramids were built around 4,500 years ago and are considered to be among the oldest and largest structures in the world.

These are just a few examples, and there are likely many more ancient structures throughout the world that predate even these oldest examples.