What is the Roman road in Jordan, southwest Asia made out of?

Answer

An example of this is found on the Roman road from Căzănești near the Iron Gates. This road was half carved into the rock, about 5 ft to 5 ft 9 in (1.5 to 1.75 m), the rest of the road, above the Danube, was made from wooden structure, projecting out of the cliff. The road functioned as a towpath, making the Danube navigable.