In the depths of the Sierra Nevada National Park (North coast of Colombia) can be found the pre-Colombian ruins.
It has been off limits to tourists for many years (and really unknown until 1972) due to the paramilitary and drug related violence as well as the 4 indigenous tribes using it as a sacred site.
To reach the site it take around 4 days (46km) to hike there, using only guided tours. All tour companies offer the same deal, some with english tour guides (so double check it first).
The hike is long (28 miles) and rather tough due to the early starts, some steep hikes combined with the heat though the jungle, river valleys of Sierra Nevada and local villages. Finishing on day 3 with a 1200 steps to the top!
For me the scenery around the trail was beautiful and more eye opening than the Lost City itself. But learning about the history of the site from our guide made this place. The actual site is believed to be built around 800AD by the Tairona people, way before the Incas built Machu Picchu. The discovery of gold and ceremic urns resulted in an interest from archaeologists and the reconstruction of the 250 terraces and 30 hectare site.
If wanting to take the treck, make sure that you bring a swimming costume to cool off in, mosquito repellent (lots!), extra clean clothes and good walking boots (aswell as flip-flops to change into in the evening). Don’t bother bringing too much as you will have to carry it for the whole trip!