Fort San Pedro is a decommissioned military defense compound adjacent to the local markets and modern day piers. Fort San Pedro was built in the 17th century and stands today as a pseudo-museum of the original Spanish settlement and how history changed during the Philippine Revolution of the 19th century.
Fort San Pedro is a [mostly] self-guided tour. You can opt to pay a nominal amount and have a local college student give you a guided tour (which we opted for). The guided tour not only gives you a unique 1:1 tour, but the tour guide received credit in school as a part of their graduation requirements.
The Fort is large open access to where ever you want to go. There are plenty of murals and information signs explaining the numerous historical significance.