A port is a maritime commercial facility which may comprise one or more wharves where ships may dock to load and discharge passengers and cargo. Whereas early ports tended to be just simple harbours, modern ports tend to be multimodal distribution hubs, with transport links using sea, river, canal, road, rail and air routes. Successful ports are located to optimize access to an active hinterland. Ideally, a port will grant easy navigation to ships, and will give shelter from wind and waves.