Some northern Provinces of Iran lie between Caspian sea and huge Alborz mountain range. Humidity from the greatest lake of the world(Caspian Sea) will be stopped by Alborz and will be transformed to rain in Gilan, Mazandaran & Golestan provinces. This most humid region of the country is almost covered by forests in foothills and pastures in altitudes. Lonak waterfall in Siahkal County is one of the uncountable landscapes of Gilan Province.