Asveja Regional Park is located on the heights of the Baltic-Švenčionys hill, which is characterized by a great variety of terrain. In this place, the glacier of the last glaciation, its melting waters and other factors formed deep, long, narrow valleys called rhines. Lake Asveja is concentrated in one of the most expressive rhines in Lithuania, and a number of other smaller ones flow into it. Parallel to the western part of Lake Asveja, the Pagrunda rhine meanders. The length of the rhine is about 1.5 km, the width is about 100 m. Its bottom is swampy, even in dry summers you can find wet places here. It is likely that the was a lake in the Pagrunda rhine thousands of years ago.