One way to find out if there are addresses associated with the two points in question is to use a g.p.s. utility or google maps. the other way is to do it manually and get a local map of the area and scale the distance using a ruler of some sort
The distance between the Hotel Mozart in Rome Italy and the port of Civitavecchia is approximately 5.6 miles. If you take the shortest route, which is Gregorio VII, you should get to your destination in 20 minutes when driving.