Graži vieta, Panevėžio apskritis
Žalsvasis šaltinis is described in Lithuanian sources as the country's deepest known spring-fed cave system, reaching a documented depth of 20 meters on the left bank of the Lėvens River in Pasvalys. It formed around 1960 when a sinkhole collapsed into the underlying limestone, and its discharge (64.24 liters per second) is among the strongest of any spring in Lithuania. The cold water carries a faint hydrogen sulfide smell and keeps a 10-12 meter stretch of the Lėvens ice-free through winter, drawing overwintering ducks; it has been protected as a hydrogeological natural monument since 2000.