San Juan Mountains, Colorado. 13,894’ Vermilion Peak looms over Hope Lake Basin in the San Juan Mountains of southwestern Colorado. This 4,000 square-mile mountain range began to rise at the beginning of the Laramide Orogeny about 60 million years ago. The scenery we see today is mostly a result of the recent ice-age glacial advances which carved deep valleys and created many of the precipitous peaks which fill this range today. The San Juan Mountains form the largest mountain range in Colorado and contain 13 summits higher than 14,000’.