Nicaragua
A Central American country that used to be notorious for its political turmoil, esp. in the 1970s and 1980s when the neo-socialist Sandinista government under Daniel Ortega, which had overthrown the previous dictatorship of the Somoza dynasty and its infamous National Guard, now battled it out with the USA-backed Contras (remember the Iran-Contra scandal?). Assassinations, death squads, scorched earth, arms and drug trafficking money used to support the Contras … it was all very nasty, and certainly one of the blackest chapters of the notoriously dubious US involvement in Latin America.
For a while the Sandinistas were eventually ousted (partly over fears that the US might otherwise openly invade the country militarily) and a shaky compromise democracy developed. This saw Daniel Ortega return to presidency in 2006.
Overall, the country has managed to stabilize remarkably – and tourism is on the up, very much so, going from virtually non-existent in the 1980s to being the single most important growth sector in the Nicaraguan economy. Its main assets are wildlife and scenery. The country uses the epithet "land of lakes and volcanoes" to promote its natural specialities: indeed, Nicaragua is home to Central America's largest lake (in turn home to the planet's only fresh-water sharks!), and also to a host of volcanoes (Masaya volcano is said to be one of the world's most accessible volcanoes). Accordingly hiking, boating and wildlife watching are high on the list of the country's tourist activities.
The volcanoes aspect may already overlap sufficiently with dark tourism to grant the country a place on this website. But there are also more properly dark sites.
The Museum of Legends and Traditions (in Spanish: Museo de Leyendas y Tradiciones) in the country's second city (and traditional leftist stronghold) of Leon is housed in a former prison from the Somoza era. Apart from a few former prison cells, the museum's exhibits are not so much related to the politics and dark sides of the struggle between military juntas and socialist revolutionaries, but rather to local legends. But still, some of these are grim enough too, and involve scythe-wielding skeletons in ghostly white shrouds and sinister things like that. And of course it's simply the location that makes it. (Opening times Tuesday to Saturday from 8 a.m. to 5 p.m. with a traditional lunch break between noon and 2 p.m.; Sundays open only in the morning).
And then there are the revolutionary murals, also mostly in Leon, which are a kind of Latin-American style version of socialist realism, while at the same time not being all that dissimilar to the famous murals of Northern Ireland. Many such murals have been lost to iconoclasm and/or neglect, but a fair number are still in place, including the walls of the Museum of Legends and Traditions, but also on a wall near Leon's large cathedral.
Furthermore, there are several other related museums about the revolution and the struggle with the Somoza National Guards and/or the Contras, including the Revolution Museum in the capital Managua (Museo de la Revolution); in the northern town of Esteli (about a hundred miles / 160 km north of Managua), there's a small museum about the revolution and the tragic events of that period called Asociación de ex-combatientes historicos ('Historical ex-combatants museum' in English); in San Rafael del Norte, north of Jinotega, there's a small museum about Nicaragua's national revolutionary hero of the 1920s/1930s Augusto Sandino (the man that the Sandindistas derived their name from).
So: lots to discover – best on guided tours, esp. if you don't speak Spanish well enough for independent travel (which can be logistically difficult in Nicaragua in any case).