The Fortress of Terezin was used as a political prison during WWI and as concentration camp during WWII, [this is a picture of the plaque at the cell where Gavrilo Princip was held for 3 years.] (http://imgur.com/SWSofYb).
Gavrilo Princip, the main participant of the assassination in Sarajevo whose victims on Vidovdan June 28. 1914. were Austro-Hungarian heir to the throne Franz Ferdinand and his wife Sofia, was kept in this solitary confinement cell from December 5. 1914. The Vidovdan Sarajevo assassination led to the first world war.
For the majority of Slavic populace in Austria-Hungary Gavrilo Princip was a symbol of fighting against the Habsburg monarchy. In Serbia he became a national hero and in the Czech countries memory of him was kept especially during Czechoslovakian Republic (1918. - 1938.) but also after the Second World War. Gavrilo Princip died from the effects of mistreatment on April 28. 1928. in the military hospital in Terezin.
Source: I'm Serbian.