This is one of the most offbeat sites that is off the tourist circuit. It is known only to locals, who will guide you through the lanes of the villages and take you underground through a tunnel. Sumur Gumuling was once a part of the Taman Sari complex and the underground cave was a mosque with a well in the centre. The word Gumuling, which means rolling, probably refers to the circular well which was used by the people for ablutions when they came to the mosque. Sitting there, you can hear the walls echo with silence, while right above the structure is a bustling little settlement.