One thing I always wondered was the Bering Strait. It's narrow, ancient civilizations sailed much further distances, there are islands between the continents, and people who knew how to make boats lived in that area. So why wasn't there any travel or trade before the discovery of the Americas and if there was, why isn't that well-known?
There was extensive trade and contact across the Bering Strait from Eurasia to North America -- it's how Native Americans and First Nations people ended up in America in the first place. There was ongoing trade up and down the coasts throughout the period of Columbus' voyage and later -- but the thing to keep in mind is that this was local trade across the strait. In games like Civilization you get a popup that says "your explorers have discovered a new continent, they are naming it America" or the like, but that's not how exploration works/worked in this period.
For much more on pre-Columbian trade and contact, this section of the FAQ should be of interest.