Elmina was built on sedimentary rock believed to be over a hundred meters deep, thus explaining why it is in such good condition today. The castle was isolated from the community with moats, over which spanned a drawbridge, allowing no one to enter of leave the castle when lifted. The Portuguese built Elmina Castle in 1482 as a trading post to house goods bartered (like guns, ammunition, tobacco, alcohol, and spices) for local gold and ivory. As the demand for slaves developed in South America (Brazil), the Caribbean Islands, and America, the castle began to store a more precious and perishable trade - African human slaves.
Millions of Africans were taken into slavery between the 1500s and 1800s. The slaves were traded or sold to Europeans sometimes by their own chiefs, by a victorious warring tribe, or native African raiders. Elmina castle could hold 600 men and 400 women and children (over age 12) for months at a time, waiting for the ships to arrive. The cramped conditions had to be atrocious.