Barcelona's most iconic building - a mustn't-miss marvel on any tour of the Catalan capital - is the fanciful Sagrada Familia, dreamed up in the late- 19th century by the visionary, if kooky, architect Antoni Gaudi. When Englishman Eric Arthur Blair visited the extravagant place of worship in 1937, however, he declared it to be "one of the most hideous buildings in the world".
Blair was not an archetypal tourist, of course, and his Homage to Catalonia - in which the writer, under his pen name George Orwell, scorns Gaudi's modernist masterpiece - is no guidebook.
Homage to Catalonia is Orwell's personal account of taking up arms to fight fascism during the Spanish civil war. The book - which no doubt makes me conspicuous as I turn its pages amid the intoxicating whirl of elegant globetrotters and boho-chic backpackers on the spacious Placa de Catalunya - kicks off with the writer's arrival in Barcelona in December 1936.
Just five months earlier, military strongman Francisco Franco had instigated a coup against republican Spain's democratically elected government, and a right-wing uprising in Barcelona on July 19 had prompted a ragtag militia of mainly anarchist trade unionists - accompanied by communists, socialists and republican police - to fight back.
After pitched battles in the Placa de Catalunya, the fascists were repelled and the city was held. What's more, the anarcho-syndicalist Confederacion Nacional del Trabajo (National Confederation of Labour) had seized 30,000 rifles. Suddenly, Barcelona's working class was heavily armed, and dreaming of all-out revolution.
Orwell wrote that he had "come to Spain with some notion of writing newspaper articles". Letters, however, reveal that - like tens of thousands of others with proletarian sympathies who would arrive from across the world (including 100 or so documented Chinese) - the writer had travelled to join the anti-fascist struggle as a volunteer. And the Barcelona he discovered in 1936 reads like another intoxicating whirl, if of a more egalitarian variety than that on display in 2013.
"It was the first time that I had ever been in a town where the working class was in the saddle," reads Orwell's initial impression of revolutionary Barcelona. "Practically every building of any size had been seized by the workers and was draped with red flags or with the red and black flag of the anarchists … even the bootblacks had been collectivized … everyone called everyone else 'comrade' … human beings were trying to behave as human beings and not as cogs in the capitalist machine."
My flaunted copy of Homage to Catalonia does its job and I'm spotted by Nick Lloyd, a Briton who has lived in Barcelona for 23 years and who runs Spanish civil war-themed tours of his adopted city (bookings via thespanishcivilwar.com  Lloyd points out that the headquarters of the Soviet-backed Partit Socialista Unificat de Catalunya (Unified Socialist Party of Catalonia) once stood at the northern perimeter of the plaza. Today, the site is home to a huge Apple flagship store.
We head south, down La Rambla, which Orwell called "the wide central artery of the town where crowds of people streamed constantly to and fro". The tree-lined pedestrian boulevard is also vibrant today, with shoppers and tourists, musicians, magicians and other street performers, and - we've been warned - a battalion of pickpockets.
Lloyd pulls out an iPad and plays aloud the anarchist anthem A Las Barricadas ("to the barricades"), inviting us to imagine that the thousands of fresh-faced folk shuffling up La Rambla in their Zara togs are, in fact, striding revolutionaries clad in blue overalls, that the cameras slung over their shoulders are really rifles.
We step off La Rambla and into the labyrinthine Barri Gotic (Gothic Quarter). At the 14th-century church of Santa Maria del Pi, Lloyd explains that the Placeta del Pi, in which the church is located, was hastily renamed, in paint-daubed words, the Placa del Milicia Desconegut - or the Square of the Unknown Militiaman. The left's graffiti was just as speedily covered up when Franco's troops re-entered the city in 1939, to be rediscovered recently, when the area was given a facelift.
The church itself, with its rose-shaped stained-glass window that is a full 10 metres in diameter, suffered from anarchist rage in 1936. Santa Maria del Pi, like many churches, was set alight in revenge for the clergy's alliance with the army. (Orwell notes in Homage to Catalonia that the Sagrada Familia avoided a similar fate: "I think the anarchists showed bad taste in not blowing it up when they had the chance.")
We visit the tranquil Placa Sant Felip Neri, its stone walls pockmarked with shrapnel scars from bombs dropped by fascist aircraft in 1938, slaughtering 42 people, including 30 children. Returning to La Rambla, we stop by the Hotel Rivoli, formerly headquarters of the anti-Stalinist Partido Obrero de Unificacion Marxista (Poum; Workers' Party of Marxist Unification), with which Orwell had signed up to fight. Lloyd relates how, by the spring of 1937, complex rivalries between political factions were tearing the anti-fascist forces apart.
Back in Barcelona on leave after three months at the front, Orwell found that the Stalinists and republican police on the one hand, and anarchist and dissident-communist fighters on the other (who just months previously had battled side by side), were now at each other's throats.
To protect the Poum headquarters from republican police holed up inside the Cafe Moka next door (today a characterless, modern eatery of the same name), for three days the writer and armed Poum colleagues covered their political base from the Poliorama cinema (these days a theatre staging plays, operas and colourful flamenco shows), directly across La Rambla. (Orwell: "I used to sit on the roof marvelling at the folly of it all.")
The rewarding three-hour tour concludes at La Llibertaria ("freedom" in Catalan), a popular bar decorated with wartime propaganda posters in the bohemian El Raval neighbourhood, but a lazy stroll back through the Barri Gotic also reveals the down-at-heel Placa de George Orwell, which was named for the writer in 1997. Youngsters whiz by on roller-skates and locals dine outside hole-in-wall tapas bars, the menu of one featuring a "George Orwell" bocadillo (sandwich) of olive paste, cooked ham, cheese and lettuce.
Having survived a fascist sniper's bullet through his neck during a second stint at the front, Orwell returned again to Barcelona to discover that Poum had been condemned by Stalin-backed communists as "objectively fascist". Its members were being chased down and imprisoned, and in some cases tortured and murdered, in "an atmosphere of suspicion, fear, uncertainty and veiled hatred". Wanted by those he had previously hailed as comrades, Orwell fled to France in June 1937, never to return. Barcelona fell to Franco's troops in January 1939. The revolution had failed.
Scholars believe Orwell's Spanish experience crystallised the notion that totalitarianism - from the left as well as the right - was his real and abiding enemy. Orwell's anti-Stalinist satire Animal Farm was penned, it's argued, in direct response to the Poum betrayal, and his conviction that, in Spain, communists loyal to Stalin turned truth on its head and instigated a reign of political terror echoes throughout his dystopian masterpiece, Nineteen Eighty-Four.
Barcelona, it seems, had influenced Orwell profoundly. Ironically, the Placa de George Orwell was one of the first places in the city to be fitted with citizen-watching CCTV cameras.
Getting there: British Airways (www.britishairways.com ) flies to London daily, with a choice of connections to Barcelona.