The sign at the trailhead says it's open year round, but back in late fall it was closed for deer hunting. Watch for signs at the trailhead.
Teter Nature Trail is a short trail through one of the wooded areas around El Dorado Lake. This well-designed trail is great for a quick run. There's one steep section, and some argue that it would benefit from a small reroute to build a switchback.
The trail takes you down through woods and it has a natural spring mid-way through. There is no set direction to take the loop at the end of the trail, as you lose/gain the same elevation either way. A Kansas State Parks Vehicle Pass is required for parking in the lot at the trailhead. A nice restroom was built fall 2015 at the trailhead.