Just behind the Tsarevokokshaisk Kremlin is the Gulag Museum which is probably one of the best museums in the country detailing the system of Soviet forced labour camps.  The museum is located in what were once the NKVD headquarters in the city where prisoners were interrogated before being sent onto a camp.  The rooms are now brimming with all sorts of items connected with the Gulag and the Soviet era.  This includes many statues of Stalin, Lenin and other revolutionaries, as well as clothing and items of Gulag prisoners.   The museum also has details on various prisoners who were interrogated here and on those who conducted the interrogation. It has also collected information and photos of mass graves in the Republic of Mari El.  

In addition it has become a repository of various items from a pre-Revolution Yoshkar-Ola which would have otherwise been disposed of, such as old gravestones and farming equipment.  The staff at the museum prefer that people visit as part of a guided tour as otherwise you would be lost among all the exhibits, but it is possible to join an already on-going tour or leave earlier if you are short of time.  It is free to enter, but a donation is requested.