The city of Porto, Portugal has many historic buildings, but for fans of transport history, the three remaining lines of the Porto Tram System are a thing of wonder. 

The Porto Tram Museum is located by the Douro River and houses several overhead electric-powered streetcars (and some horse-drawn examples), but the fact that these historic vehicles still provide a public service in the city is a tribute to their craftsmanship. Very much like the San Francisco cable cars, they are both a tourist attraction and a means of transportation around the city. The cars range from 19th to early 20th-century examples, the variety is enormous.

The system was established in 1872 and electric power was introduced in 1895. Before that time, all the cars were pulled by mules, with the last of these mule-drawn trams going out of service in 1904. Occasionally, the museum runs its historic mule-drawn trams on Route 1, but they are now pulled by horses.

After a gradual decline as cheaper buses took over, 22 lines of this service were reduced to a single heritage line in 1996. Since then, two extra heritage service lines have been reinstated. Line 18 travels from the museum to the city center and back down again.