Otjikoto Lake is an amazing natural wonder situated in Namibia. The lake is one of only two existing permanent lakes that can be found in this beautiful African country. It was created by a collapsing karst cave and is a breathtakingly beautiful sinkhole located 20km north-west of Tsumeb. Otjikoto measures 102m in diameter, with a maximum depth of 91m and has a mysterious legend associated with it - local stories have claimed that German troops during World War I dumped a sealed safe into the lake and it remains to be discovered! It's not a public lake and you need diving guides to be able to dive in it.