Car rental is a great way to travel in Puerto Rico since you don't have to rely on public transport and can go at your own pace. While in San Juan, you can pay a visit to the Castillo de San Felipe del Morro, the impressive castle that has protected San Juan for over 400 years. Taking a drive outside the city limits, you can reach the national park area of El Yunque and delve into the lush tropical rainforest. Another popular destination that can be easily reached by car is the Rio Camuy Cave Park. Take a tour through the third-largest cave system in the world and see impressive caverns and an underground river. When you choose Sixt for car rental in Puerto Rico, you are free to pick your own itinerary.