Manhattan is completely surrounded by water, an easy thing to forget in this age of bridges and tunnels, but until the late 19th century residents relied completely on ferries to get between Manhattan, Brooklyn, Staten Island, and New Jersey. Manhattan businessmen who lived in Brooklyn were occasionally prevented from working in the winter when the East River froze over. Today, bridges have made the ferries of the East River obsolete, but boats still ply some routes. The Staten Island Ferry, which serves as a continuation of the subway system, offers spectacular views of Manhattan’s harbor.