Lake Tsivlos, a mountainous and deep lake, is located at the foot of Mount Helmos (and within the limits of Helmos-Vouraikos National Park) near Zarouchla in Akrata region and is surrounded by forests. It was formed in 1913, when a landslide in the area (where the Sylivaina village was destroyed) blocked the flow of Krathis river in the valley. The initial maximum depth of the lake, just after its creation, was 77 meters, but today, after the silt that the lake has got for the last 100 years, is approximately 50 meters. Lake Tsivlos remains today a very deep lake with steep banks, and its extent and coastline fluctuate, as the water level goes up and down depending on the season and the amount of rainfall each year.

The lake today is fed by mountain streams of Krathis river upstream (eg, » Waters of Styx River”, ravines and streams from the surrounding slopes) and at least by two springs located below its surface. The lake is located at such an altitude, where the two different forest vegetation zones meet: the flat one with the Aleppo pine and the mountainous one with the black pine and the spruce. Nowadays, forests of pines dominate around the lake with black pines – Pinus nigra, Kefalonian spruce -Abies cephallonica, Aleppo pines – Pinus halepensis, wild cedars -Juniperus oxycedrus, yews – Quercus coccifera, mountain oaks – Qurcus pubescens, and in gullies and around the lake forests with willows , plane trees, sedges and others.

«Lakes in Greece. Narrations and records», Dr. Theodoros Kousouris, ΕΚΚΕ 2013