One of Poland's finest examples of military architecture, the citadel was built by Tsar Nicholas I between 1832 and 1836 after putting down the November uprising, and was used as a jail and place of execution for Polish patriots. One section is now a park, another remains in military use. Several museums are planned to be established here in a bid to chart the history of Poland. For the moment, Katyń Museum is devoted to the Eastern Polish Front during the Second World War.