The Sierra Nevada de Santa Marta is the defining fact: Pico Cristóbal Colón and Pico Simón Bolívar reach about 5,700 m roughly 42 km from the Caribbean, which makes it the highest coastal range in the world. You can see snow and palm from one spot. You cannot walk up it. The páramo, high lagoons, and nevados are closed to tourism by the park authority and by the Arhuaco, Kogui, Wiwa, and Kankuamo authorities who hold the range as sacred ground.
What is open is extraordinary on its own terms. Teyuna — Ciudad Perdida — was built from around the 8th century by the Tairona, several hundred years before Machu Picchu, and is reached only on foot up the Buritaca. In the coffee belt, the Valle de Cocora holds the Quindío wax palm, the tallest palm in the world at up to 60 m, standing out of cloud on open pasture at 2,400 m where palms have no business being.
Country-level constraints that decide whether a date is possible.