The Marble Caves (Capillas de Mármol) are a group of sculpted caves in the General Carrera Lake, showcasing stunning formations of marble. Access is primarily by boat, typically from Puerto Rio Tranquilo, making accessibility limited for those with mobility issues. Tours are almost essential, as navigating the lake and caves independently is difficult and potentially dangerous; solo exploration is not recommended. The best time to visit is during the warmer months (November to March) when the weather is more predictable and the lake is calmer. A boat tour typically costs between $20 to $50 USD per person, and the duration is usually 2 to 4 hours, depending on the tour operator and weather conditions. The vibrant colors of the marble are most striking when the water level is lower and the sun reflects within the caves.