The Great Divide
This expansive frozen wasteland just north of the City of Vinheim essentially serves as a barrier of passage between the southern lowlands and the northern highlands. Recurring blizzards blow through the valley on a near-constant basis, making travel through the region extremely hazardous. Due to the raging winds and blinding snow, visibility is typically severely compromised. The only benefit of such strong winds is that they seem to keep the mists at bay, so at the very least the threat of being consumed by the mists is minimal while traveling through the valley.
As the Frigid Valley is the only place known to be free of the pervasive mists, it has become a major trade route, despite the myriad natural dangers it presents. A railroad connecting Vinheim and the City of Barovia runs straight through the Frigid Valley, though securing passage aboard the train is typically very expensive. Nonetheless, traders are more than willing to pay the fare to avoid having to trek through the frozen wastelands by foot.
Notably, the Frigid Valley is also the ancestral home of the Icewalker Tribe, a tribe of savage frost giant warriors.