Lake Ohrid is one of the world's oldest lakes, formed millions of years ago on the western side of the Dinaric Alps by geotectonic depressions (as were similarly ancient lakes Titicaca in Peru and Baikal in Siberia). This ancient body of water is home to the European eel, which comes to Lake Ohrid from its birthplace thousands of miles away in the Sargasso Sea. The eel lives in Lake Ohrid for 10 years, then returns to the Sargasso to spawn and die, leaving its progeny to repeat the process after birth.
The earliest scientific studies, undertaken in the course of the 19th century, showed that, as one of the oldest lakes in the world, it has preserved primeval life - forms which no longer exist in other places or only exist as fossils. The importance of the lake was further emphasized when it was declared a World Heritage site by UNESCO in 1979 and when, in 2010, NASA decided to name one of Titan's lakes after Lake Ohrid.