A Santa Marta agency that has organised itself like a company rather than a shopfront: the contact page lists five departments with their own numbers and mailboxes, and separates retail customers from trade. If you are a traveller, the B2C line is the one you want.
Ciudad Perdida in three, four, five or six days, plus the Tayrona park, the Don Diego river, and multi-day walks to the Bunkuany and Gotsezhy settlements in the high Sierra that most agencies do not sell at all.
The four-day trek leaves at 07:30 and costs the standard COP 1,860,000. The three-day express leaves at 04:00 and costs more, at COP 2,200,000, which tells you what compressing the walk actually buys.