Pikku-Vesijärvi is an English-style arboretum that was made in the 1950s on Lahti Manor land. The park has many species of trees, and over the years has become Lahti’s most important greenery area. A wide variety of events are held in the park, including the Kariranta summer theatre. The park is also home to the largest water organ in the Nordic countries.
There is a musical fountain in Pikku-Vesijärvi pond and the show consists of music and spectacular water jets. There are a couple of performances per day in the summertime without the coloured lights.