Island of Seven Cites by Paul Chiasson

Sub Title Where the Chinese Settled when they discovered America. The author discovered a big, previously unknown stone walled settlement at the top of Cape Breton Island. It's in the gulf of St Lawrence, right on the northern end of Novia Scotia. The author gives a solid, spare no obscure reference, review of European exploration records of the area, going back before Columbus, and finds no mention of a European settlement on the spot. He suggests that Chinese voyagers from the heroic era of Zhang He (1400's) settled on Cape Breton to work a gold mine. He points to strong Chinese influences on the local Micmac Indians, matters of dress, advanced knowledge of navigation, sailing, and medicine. The Chinese were sailing to East Africa, and there is a Chinese map from the 1400's showing both sides of Africa, good evidence that they had rounded the Cape of Good Hope, a century before Bartholomew Diaz.
Chiasson points to favorable ocean currents that could carry a ship from Cape of Good Hope to the St Lawrence. The Chinese vessels were capable of round trip voyages from China to East Africa. Any ship with that sort of range could make the trip from an East African harbor to Canada.
Personally, I feel the voyage length is extreme, and there are plenty of more inviting sites to settle in North America than Cape Breton Island. Also, the Atlantic westerly winds would sooner or later drive a Canada bound Chinese vessel into a European port.
Since, it's a fascinating thesis, and the site on Cape Breton Island deserves excavation by a professional archeologist.