This page will have a guide to the treasure map you find in Havana in Assassin's Creed IV Black Flag
Treasure Map Location[edit]
The treasure map itself can be found in a Cadaver near a monastery at the northern part of the island. The Cadaver is hidden inside some bushes, near a stone fence, see below for map and screenshot of cadaver location:
Treasure Map Tool[edit]
This is the treasure map you find:
Coordinates indicate (240,607) which are just the coordinates for Havana. The Red X marks the spot where you should dig
Dig Site Location[edit]
Set a custom marker on the south shore, to the right of the stone tower, as seen in this map:
The dig site is near the edge of a fallen down tree, at the based of some stone steps. See screenshot below for help. Just walk around there until the option to dig appears:
You will get 3,000 Reales and design plans for Queen Anne's Figurehead: