The snow melts on the Rocky Mountains to reveal wildflowers blooms, serene alpine lakes and burly waterfalls. Hiking trails here range from easy-peasy and pleasant to thigh-burning day-long challenges. The Iowa Hill Loop is a pleasant stroll through an 1800s placer mine site and at 3mi (4.8km) long, it’s more popular with history buffs than hardcore hikers. At the other end of the spectrum is Quandary Peak: a rigorous hike that’s only 6mi (9.6km) long, but climbs vertically up 3,305ft (1007m). It will take you anywhere from three to nine hours to complete.