Šilo and Žolyno Streets were constructed at the bottom of the deep and wide arroyos that used to be called Sapiegos Gullies. Žolyno Street ends at the Iškartai Eroded Hills reminding of a branching out fan. This is a unique and picturesque steep-walled labyrinth of arroyos and gullies.
As you walk in the area, guessing the origins of this intriguing landscape is not that hard: each dry valley starts with a high and steep circle-shaped slope reminding of a circus tent. Long ago, a spring erupted at the bottom of this circle-shaped hill only to later turn into a stream. The slope was constantly washed away by the spring and thus continued to deteriorate and retreat upwards while the stream carried the soil away. An interesting fact is that all the dried out valleys, old gullies and arroyos formed in the eroded hills seem to be located on the third river terrace. This means that both the eroded hills and the river terrace were shaped together approximately 13,000 years ago.
For a long time, the proglacial lake has been at the level of the third river terrace. The period was very important in the history of the formation of the surface of Vilnius region as this was the time when the slopes got most trenched, the eroded hills were shaped and forests grew upon the climate getting warmer. Iškartai Eroded Hills are protected under the Iškartai Natural Reserve.
The Lyglaukiai Geomorphological Reserve was established to protect the longest eroded ridges in Lithuania. These ridges comprise a long-shaped positive relief that stands out higher than the medium. The ridges are sediments that have remained among the many gullies and valleys formed by waterways. The Pavilnys Regional Park has the following four eroded ridges: the Large Lyglaukiai, the Small Lyglaukiai, Sapieginė and Šveicarija (Switzerland). The Large Lyglaukiai Ridge is the longest, flat-surfaced and overgrown with an old forest. The ridge opens up to mesmerizing vistas of dry valleys and hills beyond the Vilnia River and Vilnius City. This ridge is the one most affected by industrial works, digging and construction. The Sapieginė Ridge is the most natural of all ridges, though it too hides the remains of defensive structures and fortifications.