The Timberline Trial hike is a shorter hike to a beautiful lake near Leadville. The big lake is one of my favorites with many areas to enjoy.
One of the best parts of Colorado hiking is alpine lakes. The Ptarmigan Lake Trail is a moderate hike full of wildflowers and a great lake.
Bierstadt Lake in Rocky Mountain National Park is a moderate hike that has amazing views and a mountain lake surrounded by forest.