With a dozen tall ships arriving in Boston Harbor in a few days, Sail Boston said four-million visitors are expected between July 11th and 16th.

Organizers note there will be street closures for Saturday's Parade of Sail and use of public transportation is strongly advised.  Subway lines will operate at maximum level and there will be shuttle buses between JFK/UMass and Castle Island. 

There will be designated viewing locations in Charlestown, Castle Island, the downtown waterfront, East Boston, and the Seaport District.