Johann Strauss Junior's rousing waltz, first performed on February 15, 1867, is now one of the world's most famous and catchiest pieces of classical music. It features in movies galore and danced to still.
"An der schönen, blauen Donau", as it is known in the original German, began life as a choral work commissioned by the Vienna Men's Choral Society. The main aim was to cheer people up after Austria had lost an important and bloody battle against Prussia, at Königgrätz, the previous summer. The title was said to have been inspired by a poem but the words were penned by the society's own lyricist, a policeman who humorously bemoaned the state of the defeated country. It was not an immediate runaway success, although an exhibition marking the anniversary at Vienna City Hall seeks to refute the belief that it was a total flop.
One glowing contemporary account even calls it a "schlager" (German for "hit") - supposedly the first recorded use of the term. But the piece only really took off once an orchestral version was performed in Paris later in 1867, to a rapturous reception, and soon afterwards in London. In a tour of the United States in 1872, Strauss conducted a performance by a 2,000-piece orchestra and a 20,000-strong choir to 100,000 people.
Today "The Blue Danube" evokes like no other waltz the elegance of Vienna's 19th-century heyday - which lives on in the city's ball season, currently in full swing. It also takes pride of place in the Vienna New Year's Concert every January 1, and is Austria's unofficial national anthem. When Austria declared its independence from Nazi Germany in April 1945, it was "The Blue Danube" that was performed since at the time the country had no official national anthem of its own.
The national airline Austrian Airlines plays the music to passengers before takeoff and after landing. A survey in 2016 of customers found 72 percent in favour of the practice continuing.
It is also a perennial favourite on the silver screen, most famously in Stanley Kubrick's "2001: A Space Odyssey" but also in "Cool Runnings" and "Titanic", to name but a few.
More irreverently, a sketch by British comedy troupe Monty Python showed members of an orchestra exploding one by one as they played the piece in a field.
It has also featured in madcap animated series "SpongeBob SquarePants" while in "The Simpsons", Homer, in homage to Kubrick, floats around a spaceship eating potato chips.
But apart from it simply being a nice tune, how to explain the popularity, particularly considering that Strauss wrote almost 500 other waltzes? "There is no definitive answer," Thomas Aigner, curator at the City Hall exhibition, told. "It's a patriotic song, but not too much. Everyone can project their own memory linked to the river, to a visit to Vienna."