here is a lot of beauty under the ground of Pegunungan kidul jogjakarta, here, one of the most important karst ecosystems in indonesia gunung kidul karst save the backup of water, the source of people’s lives on it and for several years. cave explore activities become something useful for local wisdom. some caves have functioned as the special interest tourism, adventure touris. jomblang cave (javaindoecotourism.com) and grubug cave (javaindoecotourism.com) in wonosari gunung kidul become one of them. the most sought after in this place is the fall of thousands light into the underground river at a depth of 100 meters grubug hole. we called it ray of light.to reach the underground  river. we must go down and up with the help of ropes. for beginner, easy techniques is necessary.