Look around and you will see the primary reason this city remains so well-preserved: its massive walls. These fortifications were not built overnight. In fact, it took over 200 years of painstaking labor to complete the eleven-kilometer perimeter that circles the historic center today. The construction was sparked by a series of devastating pirate attacks, most notably in 1586, when the English privateer Sir Francis Drake held the city for ransom, destroying over 200 houses. To prevent this from ever happening again, the Spanish Crown invested more than 20 million Spanish reales—an astronomical sum at the time—to create this military marvel. As you walk, reach out and touch the stone. You will feel the rough texture of coral stone, which was harvested from the nearby sea. These walls are up to 12 meters high and nearly 20 meters thick at their base, making Cartagena virtually impregnable during its heyday. A practical tip for you: the best place to appreciate the scale of this engineering is at the San Francisco Javier bastion, where you can see the cannons still pointing out toward the blue horizon.