He died May 23, 1885 in what was then known as Derpt, which was a city in Imperial Russia. Courtesy the treaty of Nystad (then Swedish; now the Finnish city of Uusikaupunki, in the south-west) in 1721 much of Swedish Estonia, Ingria (where St. Petersburg, also known as Leningrad, stands), Livonia (southern Estonia plus northern Latvia) and portions of Finland were sold to Russia for two million silver thalers. Among other things, the treaty effectively marked the end of the Swedish Empire and the ascent of the Russian Empire. The city of Derpt was eventually renamed Yuryev in 1893.
After World War I Estonia broke free of Russia and the city was named Tartu. In the 1920 peace treaty between the Bolsheviks and the Estonians Russia renounced all claims to Estonia “forever”. Forever turned out to be 20 years – the Soviets reoccupied Estonia as part of their 1939 treaty with Germany.
Tartu kept its name and the Soviet Union kept Estonia until 1991.
During all this there was a very good department of astronomy at the University of Tartu. The old observatory was preserved and is shown below.