Colombia:
Medellin - hottest women, nice weather, good nightlife. a good pad to explore the rest of colombia and south america. home to pablo escobar.
Cartagena - more touristy but a world heritage listed old town surrounded by fortifications. built by the spanish as a port to ship out all the inca gold they stole. pirates and bucaneers would sit off the coast and sink the ships.
La Ciudad Perdida - The lost city - ruins that pre-date Macchu Picchu and are only 10% uncovered. Cool 5 day hike with hardly any others on the trail. Used to be able to do a cocaine factory tour but the Colombian military shut that down.
Rio Hacha / La Guajira - the northern most point of South America. Remote beaches, desert, fresh fish every night and a unique Caribbean vibe.
Bogota - the capital - normally pretty cold but it's good to acclimatise if you're heading south to do the Inca Trail. Has some cool museums and good nightlife if you know where to look.