We brought our dog on our vacation to St. Augustine recently. The Castillo de San Marcos fort in St. Augustine is dog friendly but just on the outside grounds not inside the fort. 🐕The fort was completed in 1695. It is the oldest and largest masonry fort in the continental United States. It was attacked several times and besieged twice. The fort stood up against multiple attacks of cannonball. You can still see the holes. It is made of coquina – a soft limestone made of shells. 🐚 I love this fort. I have to visit it every time I visit St. Augustine. For the ghost tour fans out there – the fort might be haunted. It was featured on the Travel Channel’s Ghost Hunters TV show. The ghost stories involve love triangles, soldiers and when the fort was used as a military prison.