The fortifications of Copenhagen underwent a comprehensive modernization and expansion in the 17th century. The project was commenced and was largely the masterplan of Christian IV in the early 17th century but was continued and completed by his successors. The new fortifications relied on the existing, medieval fortifications of the city but the fortified area was extended and a defensive ring around the city completed particularly with new edifices facing the sea. The ring fortification consisted of four bastioned ramparts and an annexed citadel as well as various outworks.