People don’t think of Moscow for winter, but it’s such a wonderful time to be there. The weather is no worse than what you’d find in New York City, and the huge advantage is the people—or, really, the lack of people! No masses of tourist buses descending on the Kremlin, no huge lines for museums (of course, we ensure our travelers skip all museum lines anyway), and no crazy crowds in Red Square. Something magical happens in Moscow in the off-season: It actually becomes more approachable and less intimidating. (Plus, December falls in the heart of the theater season, so for culture vultures this is the best time to visit.)
By early December the rainy season is pretty much over in Cartagena, and it cools down just a bit more as well, so the weather really doesn't get any better than this. As with most others on this list, right around Christmas you'll find that hotels get more expensive and are more crowded, so if you can go earlier in the month you'll be paying less and dealing with fewer crowds.
In Rome, the Coliseum and Ancient Rome are outdoors, but the city also doesn’t get as cold as the others so most likely you’ll be fine if you bundle up a bit. In Venice, they often have those floods during December, but they come and go every 6 hours so even if you get unlucky you’ll still be able to get around half the day, and it’s a small city anyway.
Hotel prices definitely go up in around Christmas so it's best to come early in the month if that's possible, but it's still a pretty good bargain even during the peak weeks. Book early if you can because the better and cheaper hotels will fill up first, of course. Also consider a side trip to the Mendoza wine region, Patagonia, or the amazing water falls of Iguazu.
Plus, Colorado is home to the world-renowned Breckinridge, a historic town at the base of the Rocky Mountains’ Tenmile Range that’s well-known for its ski resort, year-round alpine activities, and Gold Rush history. You’ll also find tons of shops, galleries, and restaurants housed inside colorfully-painted Victorian buildings, along with four whole mountain peaks that provide 2,358 acres of enough variety to suit even the most seasoned of skiers, boarders, or even snow-shoers. It’s also important to mention that last season, the Summit County municipality saw 447 inches of snow. Lifts open up in November, so what are you waiting for?!