Hamamatsu sits between the Pacific and Lake Hamana, west of Shizuoka city. It is a working Japanese city rather than a polished showpiece, but that is part of the appeal: Yamaha, Kawai, and Roland give it a real musical-instrument identity, Tokugawa Ieyasu gives it historical weight, and the coast breaks into a broad belt of sand dunes.
Start near the station at the Hamamatsu Museum of Musical Instruments, the clearest expression of the city's "City of Music" claim. From there it is an easy hop to Hamamatsu Castle, where Ieyasu lived before becoming shogun. The keep is reconstructed, but the park and stone base still give the place a proper centre of gravity.
Hamamatsu is strongest when you mix the city with its edges. Nakatajima Sand Dunes feel surprisingly wild for somewhere reached by bus, while Lake Hamana brings onsen, eel restaurants, boat rides, and small side trips. It makes a good one-day stop between Nagoya and Shizuoka if you want something less obvious than another castle town.