Most lakes on Earth are quite young - they were carved out by glaciers during the last Ice Age, only a few tens of thousands of years ago. Lake Ohrid is different. It has been around long enough for its fish, snails, and tiny lake creatures to slowly become their own special kinds, found in this lake and nowhere else on the planet.
Scientists have counted over 200 species in Lake Ohrid that don't exist in any other lake. The most famous is the Ohrid trout, a kind of fish that has lived there for as long as the lake itself. The water is also unusually clear - on a calm day you can sometimes see 20 metres straight down.
On the Albanian side of the lake there is a town called Pogradec, where children swim in the lake in summer and skate on its very edges in cold winters. Some families have lived near the lake for many generations. They tell visitors that the lake is so old it has 'seen the dinosaurs leave and come back as birds'.
Because Lake Ohrid is so special, it is on a UNESCO list of places the whole world has agreed to protect. People are careful not to put too many boats on it, and they keep the water as clean as possible so the special fish can keep living there for the next million years.