Las Cárcavas in Patones, Community of Madrid, Spain, is a cool spot for a challenging hike just an hour away from Madrid. It's like a mini Bryce Canyon with interesting geological formations caused by erosion. The trail can be a bit tricky in parts, especially the descent, but the views are totally worth it. Plus, you'll likely have the place to yourself, so it's a great way to escape the city hustle and bustle for a few hours.