(230325) -- ZANZIBAR, March 25, 2023 (Xinhua) -- Photos of slaves are seen at the East African Slave Trade Exhibit in Zanzibar, Tanzania, Feb. 23, 2023. Zanzibar was once an important transit port in East Africa. From the late 18th century to the early 19th century, it became the largest slave market in the region and the last to be closed in the world. A small portion of Zanzibar's slave trade market sites has been preserved to remind people of the dark history. The UN International Day of Remembrance of the Victims of Slavery and the Transatlantic Slave Trade is observed on March 25 each year. (Xinhua/Dong Jianghui)