On the left coast of Nemunas river lies Jonionys stones. Archeologists and paleontologists believe it to be an ancient calendar meant to monitor the position of the Sun. Bigger rocks are oriented to the east and represent day and night equinox (happens on 21st of March and 22nd of September), while smaller boulders reflect Sun solstice (December 21st and June 21st). Rocks form two partially separate circles, bigger being placed in the center.
Nowadays, this location is popular sightseeing destination and is frequently used to celebrate Joninės, Sun solstice on June 21st.