Patarei is a 19th-century sea fortress turned prison, decommissioned in 2002 after more than 80 years of use and opened to visitors as a dark history museum. The star-shaped fortification on the Kalamaja shore was built by the Russian Imperial Army in the 1820s; the Estonians converted it to a prison after independence in 1920, and the Soviets continued using it through the occupation decades.
The interior has been preserved largely in its post-2002 state — peeling walls, rusting fixtures, intact cells — which gives the experience a raw authenticity that more polished history museums cannot match. The exhibition covers both the Tsarist military period and the Soviet prison years, with particular attention to the political prisoners held here. It is not for everyone, but it is serious and worth the visit for those willing to engage with it. Located on the coast near the Seaplane Harbour.