St Augustine in Florida was founded in 1565 by Spanish explorers, making it the oldest city in the United States. The unique history of this northeast Floridian city makes it a fascinating destination for a trip, especially for history buffs. St. Augustine is home to plenty of amazing architectural sites, including the 17th century fortress of Castillo de San Marcos, the Lightner Museum, which was a hotel in the 1800s but now hosts a huge array of historical artifacts within its walls, and the Spanish colonial homes and buildings that line the streets of the oldest parts of the city.