Now a group of artists and volunteers are reclaiming the walls by painting them with cheerful designs aimed at bringing some happiness and pride back to an often violent, chaotic and corrupt city.
Karachi, Pakistan's economic capital and biggest metropolis, has been swamped in recent years by a wave of extortion, murder and kidnapping -- for religious, criminal, ethnic and political reasons.
Those behind the new project, called "Reimaging the walls of Karachi" hope that by taking art to the streets they can bring a more positive outlook for its 20 million inhabitants.
"We are working together and taking back the city by reclaiming the walls which are filled with hate graffiti," artist Norayya Shaikh Nabi told AFP while drawing an abstract of the city on a wall along a busy road.
Nabi, an art teacher at the Indus Valley School of Art and Architecture, is one of 200 artists, artisans and labourers taking part in the project.
With help from the city authorities to get the permission they need, they aim to repaint walls in 1,600 different places -- from warehouses to schools to flyovers and underpasses.
The scheme is being run by I Am Karachi, a charity working for the cultural, social and literary uplift of the city, backed by funds from the US Agency for International Development.
Rare street art
Pakistan boasts some talented young artists, but public art is rare.
Munawar Ali Syed, who is leading the team of artists, said it was a pleasure to take their work beyond the elite circles of galleries and graduate shows.
"It's important for society to remain involved with art and music, but unfortunately such things are waning from our culture," Syed told AFP.
"In my 17-year art practice in the galleries, I have enjoyed working here the most as I am directly communicating with my viewers."
Under Syed's watchful eye, a team of artists use stencils to create images of boys flying kites, donkey cart races and other images of rural life.
Elsewhere, flamboyant, brightly coloured paintings of peacocks and elephants have not only radically changed the feel of Karachi but have also drawn foreigners, who usually move with extreme caution around what is a volatile city.
In this photograph taken on May 31, 2015, a Pakistani family looks at art work on a wall on a commercial street in the southern port city of Karachi. - AFP PHOTO / Asif HASSAN
Aside from daily murders, Karachi was hit by two major terror attacks in just over a year.A Taliban attack on the airport left 38 people dead last year June, and in May this year gunmen slaughtered 45 minority Shiite Muslims on a bus. It was the first attack in Pakistan to be claimed by the Islamic State group.
The project's coordinator Adeela Suleman said she was delighted the work had brought a "less hostile" look
Schoolchildren have also been made part of the project, in the hope of shifting a sense of ownership of the city and its appearance on to the younger generations.
"We included younger people so they can carry this work on further," said Nabi, as she worked with her teenage daughter on a wall.
"When they grow up they will feel that they are comfortable in sort of working for the city -- this is like planting a seed to the next generations."
The artists hope the project will subtly change people's behaviour after years of violence, softening them a little.
"I believe that this will yield good results in the long term," Syed said.
"When you see positive things around you so your behaviour becomes positive and a big change comes along in one's life."
