The massive stone structure was built by up to 20,000 workers between 1805 and 1820 as part of a system of fortifications designed to keep the newly independent nation of Haiti safe from French incursions. The Citadel was built several kilometres inland, and atop the 900 metres (3,000 ft) Bonnet a L’Eveque mountain, to deter attacks and to provide a lookout into the nearby valleys. Cap-Haïtien and the adjoining Atlantic Ocean are visible from the roof of the fortress.