The extreme conditions in the deep sea require elaborate methods and technologies to endure them. In the 20th century, deep-sea exploration advanced considerably through a series of technological inventions, ranging from the sonar system, which can detect the presence of objects underwater through the use of sound, to manned deep-diving submersibles. In 1960, Jacques Piccard and United States Navy Lieutenant Donald Walsh descended in the bathyscaphe "Trieste" into the deepest part of the world's oceans, the Mariana Trench. In 2018, , piloted by Victor Vescovo, completed the first mission to the deepest point of the Atlantic Ocean, diving below the ocean surface to the base of the Puerto Rico Trench. With the advent of satellite imagery and aviation, exploration of the surface of Earth has largely ceased, however the culture of many disconnected tribes still remain undocumented and left to be explored. Urban exploration is the exploration of manmade structures, usually abandoned ruins or hidden components of the manmade environment.