Alaska (USA) and Siberia (Russia) are separated by the Bering Strait, a narrow passage between the Seward Peninsula (Alaska) and the Chukchi Peninsula (Russia). At its narrowest point, the strait is only 85 kilometers (53 miles) wide.
On a clear day, you can see the Russian coast from Alaska's Cape Prince of Wales—and vice versa. During winter, the strait freezes, theoretically allowing an ice crossing (though politically and practically impossible today).
This proximity underscores the deep historical and ecological connections between the two continents, from ancient human migrations to shared marine ecosystems.