Muddy Creek on Weddle's Mill Rd

This was an early route of Kentucky settlers which starts at the mouth of Muddy Creek on the Kentucky River, travels through Doylesville to Union City, and then on towards Richmond.
On this section of the creek, close to the bend that's seen in the footage, I found an old, built-up road bed, about 20 ft in width, which was lined on either side with laid rocks walls approximately 3 1/2 ft tall. The road was barely recognizable due to heavy growth of foliage and paralleled the course of the creek for some distance. This structure was found on only one side of the creek. I figured that it must have been built-up and a bridge of some fashion attached to ease the crossing of the creek during high waters. At the bottom of the structure, within the creek bed, there is a square hole, having 8 inch sides and about 3 inches deep, cut out of the rock. About 10 ft up the creek, I found an iron rod with a diameter of 2 inches, embedded into the creek bed protruding about 4 inches. Not sure of the purpose of the hole nor rod.