Editing Tsumeb (section)

===Sinkhole lakes===
[[File:Otjikotosee.jpg|thumb|left|Lake Otjikoto]]
Near the town are two large [[sinkhole]] lakes, [[Lake Otjikoto]] and [[Lake Guinas]] ("Gwee-nus"). Guinas, at about 500 m in diameter, is somewhat larger in area than Otjikoto. A pioneering documentary movie about [[scuba diving]] in these lakes was made by [[Graham Ferreira]] in the early 1970s. The depths of the lakes are unknown, because towards the bottom both lakes disappear into lateral cave systems, so it is not possible to use a weight to sound them. Otjikoto, which has poor visibility (owing to pollution from agricultural fertilizers used nearby), is at least 60 m deep. The water in Guinas is completely clear and well over 100 m deep. Divers who have performed bounce-dives in Guinas to 80 m (strictly speaking, beyond the safe depth for such dives, especially given the altitude of the lake above sea level) have reported that there was nothing but powdery-blue water below them. Guinas has been in existence for so long that a unique species of fish, ''[[Tilapia guinasana]]'', has evolved in its waters.

When South Africa invaded [[German Southwest Africa]], today's Namibia, in 1914, the retreating German forces eventually threw all of their [[weapon]]ry and supplies into the deep waters of Otjikoto. Some of the material has been recovered for display in museums.

One of the largest and deepest underground lakes in the world lies a little to the east of Tsumeb, on farm called ''Harasib''. To reach the water in the cave one has either to [[abseil]] or to descend an ancient, hand-forged ladder that hangs free of the vertical [[Dolomite (rock)|dolomite]] walls of the cave for over 50 m. Here, too, scuba divers have descended as deep as they have dared (80 m) in the crystal-clear waters and have reported nothing but deep blue below them from one ledge of dolomite to the next with nothing discernible in the depths.