The Door Trail in Badlands National Park, South Dakota, is an easy hike through the Badlands.
The trail itself is unblazed, but is easy to follow up until a certain point. The trail will abruptly "end" without much notice, but you can continue hiking through the rocky terrain.
There's only so much to see in the Badlands along this trail, but it's fun to go off the path and to explore the rock formations and ledges.
This is one of the best hiking trails in Badlands National Park.