The Thousand Islands begin almost immediately downstream from Kingston — in fact there are 1,864 of them, straddling the Canada-US border in the St. Lawrence River. They range from substantial islands with year-round communities down to barely-submerged rocks with a single tree (the qualifying requirement for island status is at least two living trees and one square foot above the waterline year-round). The archipelago was a fashionable resort destination for wealthy Americans in the late 19th century, and the grand Boldt Castle on Heart Island, built by the owner of the Waldorf Astoria as a gift for his wife, still stands as the era's most extravagant monument.
Boat tours depart from Kingston's waterfront in summer, ranging from one-hour cruises through the inner islands to full-day trips across to the American side. The national park encompasses 21 islands with camping and walking trails. Kayaking among the islands — with their mix of ruined summer houses, working lighthouses, and wildlife — is particularly good.