Just as in the movie quoted above, a notable sight on many entry doors of Cartagena buildings was the Door Knocker or Aldabas de Puerta. Historically gracing the front doors of fine homes since ancient times in Greece and Rome, a door knocker traditionally denotes the association of the inhabitant. Door knockers in El Centro fall into four basic categories:
Lions tell us the inhabitant was affiliated with the military.

Knocker on the home of Sir Francis Drake

Almost looks like the Cowardly Lion from “The Wizard of Oz”
Reptiles like iguanas proclaim the inhabitant was aristocracy, born in Spain.

The fancy rectangle in the upper right is a mail/message box

This knocker is missing the loop that would hit on the round disk below the iguana
Sea creatures like seahorses or mermaids announced the home of a merchant who traded with others on the high seas.
Finally, the rarely seen cross in the knocker configuration indicated a Catholic Church leader lived within. These knockers were so rarely seen we never did find one to photograph.
Over the years, knockers have strayed from the four categories listed above. Some have become more specialized, identifying with the business within. As an example, the Masonic Lodge has its emblem as a knocker:
Some are just interesting and unique, like this one that defies categorization:
And of course there are some that just reflect the tastes of the current owner. Or perhaps that the occupant is very wise?