The largest man-made objects in the world are submarine communications cables. The longest stretch from San Francisco to New Zealand or SF to Japan, stretching over 5000 mi (8000 km). These submarine cables are typically 6.6 cm (2.6 in) in diameter and weigh around 10 kg (22 lb) per meter, weighing in at a total of more than 80,000 metric tons for the entire length. This may sound like a lot, but it isn't much in comparison to larger man-made objects: for instance, the Great Pyramid weighs about 3.8 million metric tons, and the newly completed Three Gorges Dam in China weighs about 34 million metric tons.

Discounting other two-dimensional objects such as rail lines, power lines, oil pipelines, and so on, some of the world's largest man-made objects are scientific experiments. For instance, the newly opened Large Hadron Collider (LHC) is a circular tunnel 26.6 km (16.5 mi) in length, buried between 50 to 175 meters (164 - 574 ft) underground, and includes over 1600 superconducting magnets. It will collide subatomic particles at to within a fraction of the velocity of light, and cost between $5 and $10 billion US Dollars to build.

Another large man-made object in the form of a scientific experiment is the IceCube neutrino detector, located at the South Pole. Consisting of a series of optical sensors deployed on strings over a kilometer long, the total size of the experiment is about a cubic kilometer.

More famously, the largest man-made object in terms of weight and 3-D volume is the Three Gorges Dam spanning the Yangtze River in China. As previously mentioned, the dam weighs about 34 million metric tons, has a length of 2,335 m (7,661 ft) a height of 185 m (607 ft), width (at the base) of 115 m (377.3 ft). A close runner-up is the Terminal 3 building at the Beijing Capital International Airport, which covers 240 acres and is nearly two miles long.