Colombia still bears the scars of nearly six decades of conflict between the state and leftist rebels led by the Revolutionary Armed Forces of Colombia (FARC) guerrilla group, which ended with a peace deal in 2016.
Drug cartels and right-wing paramilitaries were also players in the conflict, in which over one million people were murdered, according to state figures.
The peace accord granted amnesty to FARC fighters for all but a handful of crimes if they admitted guilt and agreed to lay down arms.
Current right-wing president Ivan Duque, who is barred due to term limits from seeking reelection, came to power in 2018 vowing to rewrite the accord, which many Colombians opposed.
Violence is on the rise again as areas abandoned by FARC become battle grounds for the rival guerrilla group ELN, drug cartels and FARC dissidents who rejected the peace pact.
The election campaign has also been stalked by assassination fears, with five presidential candidates having been murdered over the course of the 20th century.
Top cocaine producer
The country of 50 million on the northwest tip of South America is the world's top producer of cocaine, a legacy bequeathed by notorious drug baron Pablo Escobar, who inspired the hit Netflix series "Narcos."
Under Duque, the area given over to coca production has fallen seven percent to 143,000 hectares (353,400 acres) but higher yields mean cocaine output levels remain undented, UN figures show.
The country's biggest narco-trafficking cartel the Gulf Clan, has been flexing muscle in the run-up to the election.
It called a four-day "armed strike" that brought rural parts of the north to a standstill in revenge for the extradition of its leader to the United States in early May.
First black VP?
Some 9.3 percent of Colombia's population identifies as black but they are grossly underrepresented in politics.
An environmental activist is hoping to change that by becoming the country's first black vice president.
Francia Marquez, Petro's running mate, says she will work to improve the lives of women, black and indigenous people, peasants, the gay community and young people if the left wins power.
She is one of two black candidates for vice president, along with Luis Gilberto Murillo, running mate of centrist candidate Sergio Fajardo, who is trailing in the polls.
Garcia Marquez and Shakira
Nobel literature laureate Gabriel Garcia Marquez, who died in 2014, is one of Colombia's most famous figures, best known for his magical realism masterpiece "One Hundred Years of Solitude."
The home of cumbia music also produced one of the world's most successful Latina artists, "Waka Waka" singer Shakira.
Tensions with Venezuela
Colombia shares a 2,200-kilometer (1,350 mile) border with Venezuela and has welcomed 1.8 million Venezuelans fleeing the economic crisis in their country.
But relations between the two countries are tense, with Caracas breaking off diplomatic links after Bogota recognized opposition leader Juan Guaido as interim president in 2019 following a disputed election.