El Retiro Park is a lush oasis in the heart of Madrid, covering over 125 hectares with more than 15,000 trees. Recently named a UNESCO World Heritage Site, it's a favorite spot for locals and tourists alike to stroll, jog, or rent a rowboat on the lake. The park is dotted with interesting monuments, sculptures, and gardens, making it a perfect place to relax, explore, or enjoy a puppet show with the kids. Plus, you can't miss the oldest tree in Madrid, a 627-year-old olive tree that's definitely worth a visit!