useless-estoniafacts:

30th April is celebrated as Walpurgis Night in Estonia. On this day, people dress up as witches and light bonfires, ring bells and make a lot of noise over all to scare away the evil and celebrate the beginning of Spring.

In Tartu, Walpurgis Night starts with the procession that brings together
academic student organizations. The Mayor of Tartu and the Rector of the
University of Tartu greet the procession that the townspeople gather to
watch.

At midnight the corporations and societies open their doors and
members of student organizations visit each other.

The celebrations usually last until early hours of the next day and
can end with various entertaining activities – from a joint singing on
the streets of Tartu to a boat ride on Emajõgi – the river flowing
through the town.