The Santo Domingo Savio barrio here was once considered perhaps the most violent neighborhood in all of Latin America.
Police entered the hillside neighborhood only when they had overwhelming numbers. Young toughs maintained a tight grip by standing on a ridge, binoculars in one hand and a sub-machine gun in the other.
A five-story library now occupies that spot. The library -- which from below looks like three gigantic black boulders -- was chosen last month as the best work of new urban architecture in Spanish and Portuguese-speaking countries. Every day, more than 1,000 people use the free computers, children's play area and adult education classes.
Santo Domingo symbolizes the renaissance of Medellín, believed to have been the world's most violent city during the 1980s heyday of cocaine cartel boss Pablo Escobar and for a few years after his death in 1993, when right-wing death squads ran amok.
A few statistics tell the story: In 1991 Medellín had 6,349 homicides, 381 per 100,000 inhabitants, or nearly 18 per day.
In 2007, the body count was 653, or 26 homicides per 100,000 inhabitants, not quite two per day.
''Medellín went from fear to hope,'' said Sergio Fajardo, who served as mayor for four years until Jan. 1 and is widely credited with leading Medellín's rebirth.
Medellín is not alone. In fact, security across much of Colombia has improved since President Alvaro Uribe took office in 2002. He has the FARC guerrillas on the run, has dismantled most -- but certainly not all -- of the right-wing paramilitary groups -- and has curbed some of the worst human rights abuses by government troops.
''Medellín is emblematic of Colombia's transformation,'' John Negroponte, the U.S. Deputy Secretary of State, said at the recent gathering here of the Organization of American States. ``It is a testament to the change that Colombia has undergone.''
People everywhere in Medellín avidly discuss the transformación, about how the city of 2.1 million has dramatically improved.
But it is the residents of Santo Domingo, 10 miles from downtown, who tell the most striking stories.
Lourdes Medina said both her sons were murdered.
One son was killed 19 years ago when he refused a man's demand that he give him free merchandise at a store he owned.
The other son was murdered six years ago when he failed to pay protection money.
''This happened to a lot of families,'' said Medina, taking a moment from selling potato empanadas at a street fair to recount her sad tale.
''Now the community has been reborn. It's completely different,'' she said. ``The bad people are gone. I don't fear going outside anymore.''
An aerial gondola that ferries Santo Domingo residents up the hill represents the transformation.
Some 30,000 people use it every day, and the so-called ''Metro Cable'' connects with Medellín's Metro trains.
Consuelo Zea rode it recently.
''That's where my father was killed,'' she said, pointing down to her right.
She then pointed down to her left.
``And that's where my brother was killed.''
''Before, you were afraid to go to the store,'' said Zea, who makes a living selling sweets from a street cart. ``You'd see dead people in the street. Gun battles went on for what seemed like hours. Now I leave home every morning at 4 a.m. without worries to ride the Metro Cable.''
Murders in Medellín dropped steadily from 1991 until 1997, when they began to rise slightly as the paramilitary groups muscled in on the drug trafficking.
The rate has dropped steadily beginning in 2002. President Uribe cleaned out the paramilitaries and guerrillas who occupied the dangerous Comuna 13 neighborhood.
Then he got paramilitaries across the country to begin to hand in their guns, including 4,200 who operated in and around Medellín, Colombia's second largest city and a sister city to Fort Lauderdale.
Under Fajardo, Medellín began a unique program to give them psychological counseling, schooling to get their high school degrees and training for jobs in the workplace. The government has been giving the one-time paramilitaries monthly stipends to get by.
This is the type of progressive change championed by Fajardo, a university professor with a PhD in mathematics from the University of Wisconsin who favored blue jeans and long hair while in office.
He reformed the police force, built four library parks in addition to the one in Santo Domingo, added a second Metro Cable in another poor neighborhood, widened sidewalks in business districts to encourage foot traffic, built an interactive science museum, eliminated red tape that discouraged investment, built 10 new schools and spruced up the Botanical Garden.
In the past, 100 people might have visited the garden on a weekend day. On a recent Sunday, 100 people alone were participating in a yoga class while hundreds of others were walking the gardens and 300 more were watching street theater programs with a social message: Poor women should stop tolerating sexual abuse by men.
To be sure, Medellín remains a violent city by U.S. standards. The current murder rate is comparable to that of Detroit or Washington, Colombian authorities report.
About 10 percent of the paramilitary rank-and-file have returned to their criminal ways. And many fear that the murder rate will rise as rival gangs battle to seize a share of the cocaine business following the May extradition of the main paramilitary leader in Medellín to the United States.
Still, nobody expects a return to the days of terror.
A nondescript three-story home in a residential thoroughfare just west of downtown serves as a reminder of Medellín's changes. It was there that Colombian agents working with U.S. officials found Escobar in 1993 and gunned him down in a firefight on the roof as he tried to escape.
''Thanks to his death, Medellín has changed,'' said Luis Carlos Velásquez, a retired public works employee, who was walking by the unoccupied residence. ``The Mafia era is over. Medellín is 100 percent better.''