The Danube River is the frame of all the best Budapest views, the dividing line that gives the city its dual character, and the second longest river in Europe. It richly deserves all the songs that celebrate it.
If it weren't for the Danube River, Budapest wouldn't have its famous series of bridges, including the Széchenyi Chain Bridge, adorned by lions, and the Liberty Bridge, adorned by turuls (Hungary's mythical eagles). So important were many of these bridges to the city's character, they were rebuilt by the inhabitants after their destruction in WWII.
And if it weren't for the Danube, there would be no Margaret Island, one of the city's most beloved sites for summer picnics and music festivals.
Beyond Budapest, the river curls into a series of highly picturesque curves, winding its way past a series of towns popular as trips from the capital. There's Esztergom with its religious history and impressive basilica, Viségrad with its hilltop castle, and Szentendre and Vác with their Southern European appeal.
Pleasure boats ply the waters of the Danube in and around Budapest, and if you want to reach the Danube bend towns, there are regular ferries and hydrofoils.