Ostashkov (Russian: Оста́шков) is a town and the administrative center of Ostashkovsky District of Tver Oblast, Russia, located 199 kilometers (124 mi) west of Tver on a peninsula at the southern shore of Lake Seliger. Population: 18,088 (2010 Census); 20,660 (2002 Census); 27,401 (1989 Census).
The island of Klichen was first mentioned in a letter sent by Grand Duke Algirdas of Lithuania to the Ecumenical Patriarch of Constantinople in 1371. After the island was pillaged by Novgorod pirates several years later, two of Klichen’s surviving inhabitants, Ostashko and Timofey, moved to the mainland, where they founded the villages Ostashkovo and Timofeyevo, respectively. The former belonged to the Moscow Patriarchs, and the latter—to the Joseph-Volokolamsk Monastery. In 1770, both villages were merged into the town of Ostashkov.
Ostashkov is commonly regarded as one of the finest Russian provincial towns. Its main streets were laid out in Neoclassical style after the plans of Ivan Starov (1772). Local landmarks include the Ascension Church (1689), the Trinity Cathedral (1697), the Monastery of the Sign (1673, 1730s, 1880s), and the mid-18th century Zhitnyi Cloister. There is also a fanciful column erected by people of Ostashkov in 1787 to mark a spot where a wooden fort (1587) used to stand. The town’s pleasant architecture and attractive setting by the lake combine to make Ostashkov one of the most popular resorts in Western Russia.
The well-known Nilov Monastery is located on Stolbny Island, about 10 km north from Ostashkov. It was the place where the Ostashkov Special Camp of the NKVD was located and where roughly 6,300 Polish policemen and prisoners of war were kept prior to their execution in Tver. Approximately 4,300 of their comrades, held in Kozelsk were around this time executed in the Smolensk region, in what is now known as the Katyn massacre.