The United States and Japan are developing research submersible systems that will be able to explore the ocean floor's deepest spot: the 10,920-m Challenger Deep at the southern end of the Marianas Trench off the Mariana Islands. Sketch of the Shinkai 6500, a
Construction Time of the the Ming Wall. The Great Wall at Badaling. Over 2,000 years, many imperial dynasties and kingdoms built, rebuilt, and extended walls many times that subsequently eroded. The latest imperial construction was performed by the Ming Dynasty (1368â1644), and the length was then over 6,000 kilometers (3,700 miles).
Great Wall of China. It's hard to say how long because the Great Wall was not built in one go. In the very old time, about 900 BC, many states in China started build some long walls to defend its territory from enemies (neighbouring enemy states, or even northern nomads) . Some of these long wall could be hundreds of kilometres long.