A series of long walls have been found deep underwater near an area of the Antarctica called the Wilhelm II Coast. Some walls are over 60 miles long. There are some walls that intersect with other walls to create perfect right angles.
These features are located under 10,000 feet of water and can be found in several locations.
There are those who will insist these are digital artifacts, but the elevation profile tool indicates that the features are present in the ocean terrain.