Antero Reservoir, Reservoir in Park County, Colorado, United States

Antero Reservoir is a large lake in Colorado set in open terrain with rolling hills and views toward nearby forests. The water covers about 2,500 acres (1,010 hectares), is relatively shallow, and stays warmer than other lakes at its elevation of nearly 9,000 feet (2,743 meters), making it usable for fishing and boating throughout the year.

An earthen dam built in 1909 was the first dam on the South Platte River. Denver Water acquired the reservoir and the High Line Canal in 1924. The dam has leaked since construction and operates under state restrictions; a $17 million rehabilitation began in 2013, and Denver Water emptied the reservoir in June 2015 for significant repairs.

The reservoir takes its name from a submerged dry lake bed called Green Lake, which geologists estimated at some 300 years old when the dam was built in 1909. Today anglers fish year-round, including through the ice in winter, for rainbow trout, brook trout, cutbow, cutthroat trout, brown trout and splake stocked after the lake was refilled in 2007.

The site is easily reached via nearby Highway 24 and sits about twenty minutes by car from the small town of Hartsel, where visitors can find supplies and lodging. The area is open year-round, but visitors 16 and older need a valid fishing or hunting license, and some activities are limited to specific seasons.

The water remains unusually warm at this elevation of nearly 9,000 feet, largely because the lake is shallow, allowing the sun to heat the bottom more easily. This feature makes it a preferred spot for winter anglers and allows for ice fishing when the surface freezes.