It was more a mesh of overland routes that connected western China to Iranian highlands, steppe routes and from there over to the Black sea and Mesopotamia. This was not a direct trade route but rather a series of interconnections. Intensity probably varied a lot over time as well.

The idea of a very lucrative direct connection between China and the Mediterranean is bunk, but the connectivity, people and goods movement was there for a long, long time, on and off.