Abyss Lake is a 23.6 mile lightly trafficked out and back trail located near Bailey, Colorado that features beautiful wild flowers and is rated as difficult. The trail is primarily used for hiking, walking, camping, and backpacking and is accessible from May until October.
Abyss Lake is awesome. That said, it's not for novice hikers out for their first trip. From Guanella Pass Rd, the trail is only 17+ miles. 4000 ft of gain/loss and a lot of time above treeline means storms come in fast and can be severe. Few people cross your path beyond the 2 mile point, as is the case with most Colorado hikes.
If you like challenging yourself with big hikes and big scenery, this is your place.