More tourists visit the Northern Circuit than most other parts of the country, and with good reason. The sprawling landscapes, numerous varieties of wildlife, and fascinating cultures are facets of the Northern Circuit of Tanzania. Drier climate and rocky terrain accompany lower elevations, while misty highlands and cool air complement unusual foliage and forest dwellers. Ease of travel throughout the region is generally determined by weather conditions. Rain makes most roads slick and slow. The dry season is the most suitable time for smooth travel, dust being the only impediment. Game viewing is at its optimum in the Ngorongoro Crater and on the Serengeti Plains. The largest animal migration in the world, that of the white–bearded wildebeest, begins and ends here at various times of the year, and the alkaline lakes shimmer pink with the presence of millions of flamingos.