San Gil is a pretty colonial town in northern Colombia that has a focus on adventure travel and adventure tours. The rivers provide good whitewater rafting (up to grade 4) and canoeing opportunities, and numerous local tour operators offer adventure tours include caving, parapenting, bungee jumping, river rapelling, hiking, horseback riding and paragliding. San Gil's plaza is lively and great for people watching. There are lovely botanical gardens at Parque El Gallineral, which has a good river for bathing.
Lovely small colonial towns are nearby such as Barichara and Guane. Laid back Barichara is a lovely small colonial town that is a retreat for various artists and writers. Guane has a lovely main plaza and a good archaeological museum.
San Gil has a range of good hotels. Bella Isla is a large hotel just outside of town. Other options include Faro del Fonce (also just outside of town) and Macondo guesthouse (with an attached adventure sports company). Nearby Hacienda Macaregua offers good trekking options.
San Gil is the ideal stopping point for those travelling overland between Bogota and the Caribbean coast eg. Cartegena.