The impressive Katsaitis waterfall is found north of St. Ioannis, where the Katsaitis stream crosses the 33-million-year-old sandstone rocks of Lemnos.

The waterfall is formed by the discontinuities in the rocks caused by the movement of the Kaspakas active fault. The basin at the foot of the waterfall was formed due to the force of the falling water, which resulted in the subsiding of ground material, forming the natural plunge pool.

At the point on either side of the waterfall and the observer, the impressive alternation of geological formations is displayed. This was made by the activity of Kaspakas fault which brought the sedimentary rock of Lemnos into contact with newer volcanic rocks through multiple seismic sequences.