THE average pedestrian meandering through the colonial-era streets of Bogotá could be forgiven for missing it. But the six deranged-looking fish, spray-painted on to a garage door by the Spanish graffiti artist “Pez”, are worth a small fortune. “Several thousand euros”, says “Crisp”, my guide for the day. “Luckily, no one round here realises.” Bogotá is a South American mecca for graffiti artists. The pock-marked walls of the neighbourhood of La Candelaria in downtown Bogotá are a blank canvas to artists from all over the world. “Crisp”, a former physiotherapist from rural Australia, superglues psychedelic death masks to local apartment buildings. “DJ LU”, a trained architect, stencils dragonflies with AK-47s in place of wings. “Bastardilla”, one of the city’s few female street artists, pastes trippy stickers of matchstick children. “Stinkfish”, arguably the city’s most successful street artist, sprays portraits of the locals, with yellow faces and rainbows in their hair. Technically, it isn’t illegal to scrawl on Bogotá’s walls. In New York or London, dedicated anti-graffiti police units can land artists with hefty fines or even prison sentences. In Bogotá, local police often stop to ask questions and admire works-in-progress. Some even collaborate. After playing a show at the city’s football stadium last year, Justin Bieber was afforded a police escort as he daubed the downtown walls.

Not all artists enjoy such protection. Earlier this year muggers attacked “Crisp”, slashing his finger to the bone. The injury forced him to paint his masks with his left hand for a while. In 2011 Diego Felipe Becerra, a 16-year-old artist , was killed, shot twice in the back by a policeman, who allegedly mistook the teenager for an armed robber. His death provoked widespread protests and prompted the city’s mayor to clarify the rights of Bogotá’s graffiti artists.

An informal code exists among the grafiteros themselves, governing the way in which they operate. Artists are forbidden from painting over someone else’s work. The rule is mostly adhered to, with the notable exception of “Lik Mi”, a female designer with a penchant for slapping up stickers of copulating dogs and Kama Sutra couples.

A few of the works allude to the country’s polarised politics. DJ LU’s “piñas granadas”, or pineapple grenades, pepper the city. A mural of Jaime Garzón, a popular television comedian assassinated by paramilitaries in 1999, looms over the main road to the airport. Toxicómano ("Drug Addict"), an art collective, stencils adverts for imaginary B-movies. “Displacement: A movie that shouldn’t be seen, let alone lived” features a trilby-wearing Humphrey Bogart, scowling into the middle distance.

But there is room for lightheartedness too. “Rodez” is the artist behind a beautiful mural of migrating birds. His elaborate signature, or “tag”, features the names of all those who stopped to chat to him while the work was in progress. A former illustrator, Rodez took up street art in his forties after being inspired by his two sons, “Nomada” and “Malegría”. The family often travel and work together, weaving their animales fantásticos together to form a tripped-out tapestry of all-seeing eyes, flapping wings and flailing fish-tails.