I found these structures in a fairly inaccessible area of the creek. The oven like construction is made of bricks (which can be found around in the creek bed itself due to runoff) and mud for the seal (also probably from the creek). It also has some pieces of asphalt I think. It is located on the right hand side of the creek if you are walking upstream. The hole on the side makes it really look like it is meant for an oven. However, as you can verify, it remains unused.
Facing it, on the other side of the bank, lies another structure. It has a metal pole bent in an upside down U shape. And a series of stones forming a square whose two foremost corners meet the metal pole's two ends.
Any ideas what it is?
Images included from my picture album.