The "Secret Annex" is a hidden space located behind a movable bookcase in the building at Prinsengracht 263 in Amsterdam. It served as a refuge for Anne Frank and her family, along with four other individuals, during the Nazi occupation of the Netherlands in World War II. They lived there in hiding for over two years, from July 1942 until August 1944. The annex was a small, cramped area with limited light and space, where the occupants had to remain quiet to avoid detection. During their time in hiding, Anne Frank wrote her famous diary, which later became a significant historical document, shedding light on the experiences of Jews during the Holocaust.