Today, Boldt Castle is accessible by ferry, private boat, or by tour boat from Alexandria Bay, New York, Clayton, New York, Gananoque, Ontario, Rockport, Ontario, and Ivy Lea, Ontario. Most of the grounds and buildings can be explored by the public for a fee. Private boaters may also dock at Heart Island for free. Boldt Castle is a Port of Entry and has a U.S. Customs and Border Protection office on Heart Island. Visitors coming from Canada require appropriate identification to check in to the country, as visiting the island is considered entering the United States.