"Voluntary Town"; German: Pillkallen (1510–1938) or Schloßberg (1938–1947); Lithuanian: Pilkalnis; Polish: Pilkały[4]) is a village in Krasnoznamensky District of Kaliningrad Oblast, Russia.

The king Frederick William I of Prussia granted Pillkallen along with nearby Gumbinnen (now Gusev) town privileges in 1725, and stone church was built in 1756 using locally produced fieldstones.

With the outbreak of World War I, Pillkallen was attacked by the invading Russian Imperial Army under Lt. Gen. Khan of Nakhichevan in August 1914, and again between October 1914 and January 1915, which led to the town being almost entirely destroyed.

In 1944, during the later stages World War II when the Soviet Union had entered Germany, the area was assigned to the 3rd Belorussian Front of the Red Army.

Schloßberg was located in the section of East Prussia ceded to the Soviet Union, forming Kaliningrad Oblast, and became the administrative center of the short-lived Pilkalensky District until 1947 when Krasnoznamensky District was formed in its place, and the administrative functions moved to Krasnoznamensk as it had been less damaged during the war.

Schloßberg lost its municipal status and was renamed Dobrovolsk, meaning "voluntary town", reportedly because the German soldiers in the village eventually surrendered to the Red Army rather than continue fighting.

Although much of the town remains destroyed from World War II, it is nevertheless home to numerous memorials and cemeteries reflecting the fighting of the recent centuries.