Cartagena, Colombia + Add a trip

Torture Museum

Fascinating and perverse museum of the Spanish Inquisition and its torture devices. The Catholic Church has much to answer for.

Emeralds

Be on the lookout: guides will try to talk you into going to their "cousin's" emerald shops. You will get great emeralds at low prices, but you will be tired of dodging all of the people pushing them on you.

Budget places to stay

http://poorbuthappy.com/colombia/travel/place/cartagena/ has a great list of budget hostels and just general budget-y things to do in Cartagena.

Islas del Rosario, U$30 + U$5 in Port

Right across of the museum of the Spanish Inquisition you'll find the Gold Museum—Zenú.