Adventurous travellers are drawn to the savage beauty and rich wildlife of Patagonia. This region of contrasts and extremes, stretching across Argentina and Chile, runs from the river Colorado, south of Buenos Aires, across to the southern tip of South America. Many people go between July and April to visit the famous wildlife reserve of Peninsula Valdés, where right whales, sea elephants and other rare marine mammals come to breed in their thousands. However those going further south should visit only in the summer months if they wish to avoid temperatures that plummet to -13°F (-25°C). In villages along the valley of the Río Chubut you can explore the cultural legacy of the Welsh pioneers and nearby at Punta Tombo you can see the continent's largest penguin colony. Keen fly-fishermen come from around the world to test their skills in the region's rivers, the best known of which is the Río Gallegos. On the western fringe, along the Andes, you will find the most impressive of Patagonia's great lakes and national parks. The Parque Nacional Perito Moreno, with the aquamarine gem of Lago Belgrano, has excellent trekking possibilities as does the Parque Nacional Los Glaciares. Here visitors will find one of the world's natural wonders, the vast Perito Moreno glacier, a great river of ice that breaks off into Lake Argentino.