Acu spring of Bolēni is an ancient place of worship and an archaeological monument. It is known as Eye spring, Laimas spring and Health spring. It is believed that this spring is able to heal eye problems. The spring is located in a 8-meter deep ravine. The spring water always seems boiling and it does not freeze even in winter because, throughout the year, the water has a constant temperature of + 7°C. There is also a tray for water taking.