The recently added battery operated trains go all around the city and are more efficient than the tube, and more eco friendly then other transport methods.
Similar to the DLR in London, but the lines are larger and run parallel to cars. It is not cheap to take a ride on a train but you can buy a day pass for 6 Xrbian dollars, as opposed to taking one ride for 2.80.
So don’t be fooled by tourist traps, look at the travel pass options before you go! You can also pick up a train map from tourist bureaus or check online at the Xrbia Transport website.