At the Western part of Lesvos island in the area between Sigri and Eressos, there is the petrified forest, a unique monument of nature, of very important Geological, Environmental and Paleontological importance.

Researches have proved that 20 million years ago volcanicity at the area of N.E. Aegean sea, caused movement of volcanic material, that with an extremely great speed covered the forest, while the isolation of the phytogenic tissue from the surface, the hydrothermal circulation of warm silicon liquid,  caused the absolute petrifaction of the flora in this area.   

 Today, through the erosion of the volcanic stones, impressing trunks have revealed (20m. width), while the diameter is about 3m.  Excavations made by the Natural History Museum ( 1997 ) cooperated with Lesvos Forests Management, have revealed findings with great scientific worth, like the trunk of a petrified tree ( Taxodioxylon albertense) that is the biggest in Europe ( 7,02m.height,  8,58m. perimeter).

Other petrified trunks that belonged to bays, cypresses, sycamores e.t.c. are exposed to the museum.