San Juan de Ulúa
A fortress on a small island at the mouth of the harbour, started by the Spanish in the 16th century and added to for hundreds of years. It later served as a prison. The stone is hot by midday, so go early and bring a hat.
Go when Morning, before the sun is high.
Local tip Walk the stone passages and the open ramparts, and read the signs about its years as a prison. Bring a hat and water, and check ahead on how to reach it.


