The Bir Tawil Quadrangle is one of the World's most curious places. Located in the Nubian desert, it is disputed by Egypt and Sudan. In fact, it is disputed for NOT being part of either of these countries.
When the British created the Anglo-Egyptian condominium of Sudan in the late 19th Century, the border between the two entities was drawn at the 22nd parallel North. However, the coastal town of Halaib, just North of the parallel, was more easily reached from the South, and so the British drew a temporary administrative limit that included the Town, and a triangular-shaped territory around it, into the Condominium. This limit also briefly stretched South of the 22nd parallel, creating the Bir Tawil Quadrangle. As both modern nations want to control the coastal strip around Halaib, they consider a different line to be their border. This leaves Bir Tawil under the sovereignty of neither of those countries.