Belluno is a city in Veneto.
Belluno is accessible by train, directly from Padova (about 2h ride, 8/9€), Castelfranco Veneto (about 1h40 ride, 6/7€) and Conegliano (about 1h ride, 4.75€). To get in Belluno from all other cities (including Venice, Verona, Vicenza, Rovigo) you need to change in one of the stations above. Other train stations nearby are Ponte nelle Alpi-Polpet and Feltre, respectivly a village and a town both well connected with Belluno.
By car, you will follow motorway A27 coming from Venice, just follow the directions to Belluno and be careful to go out where just "Belluno" is written, not "Fadalto" (it's the name of the road that was used before the motorways, you can take that one too, but it's much faster and safer on the motorway) nor "Cortina" (unless you actually need to get in cortina of course). Once out of the motorway, at the big roundabout take the third exit, then go straight (you will enter the village of "Cadola"), at the next roundabout turn right over the bridge, you are entering the village of "Ponte nelle Alpi", go straight till the next roundabout and there turn left. Just go straight and you will enter Belluno.
By plane, you will land at Venezia-Marco Polo or Venezia-Treviso and then get in Belluno by train or car.
As the town itself is quite small, you can just walk if you aim to see the center. If you plan to hike in the mountains instead, or to see other villages/towns out of the center, then you can take a bus, just ask at the bus station in Belluno (opposite to the train station) for timetables and prices; by train is also possible to get to many places where you can hike; driving there is also possible, roads are quite comfortable.
Do not miss the beautiful cathedral.