I've been wondering; with the seafaring capabilities of, for example, the Genoese, Venetians, etc., how far could Europeans have sailed in the late 1200s? 1300s? Could a European adventurer, for whatever reason, have sailed to China earlier than the Portuguese did OTL?
I mean, I realise that at this time the Silk Road was open for business and European traders could do their work via Constantinople, but for argument's sake let's just assume otherwise. Could a journey south via the Cape of Good Hope have been successful before the Portuguese did it?