Since the 18th century, water elements in new forms have been added to the diversity of water elements that are very rich in the design of Ottoman gardens. One of the most commonly used elements in garden arrangements in Istanbul during this period is the grottos, which are artificial caves. Aim: Considering the examples of these structures in Istanbul, it is seen that many of them have disappeared, and those that have survived to the present day have conservation problems. It is necessary to research the design and structural plan of the grottoes, the materials used and the decoration program so that the necessary restoration and conservation work can be carried out. For this reason, this study aimed at determining the design properties of the grottoes in historical gardens in Istanbul. Method: Within the scope of the study, grottos located in Yıldız Palace, Maslak Pavilions, Beykoz Pavilion, Emirgan Grove, Abraham Pasha Grove and Mizzi Mansion garden were architecturally evaluated in detail. Result: The grottos in historical gardens in Istanbul were created by covering the surfaces of a bearing structure created using stone, brick and iron supports with a mortar, natural or artificial stones to form a cave. The basic principle in the design is to obtain a natural look. Grottoes resembled cascades with the water that usually flowed in a stepped way were also used to grow plants on them, to create a strolling area in the garden, or as a watch area. Conclusion: With this study, it has been observed that in order to protect the grottos in the historical gardens of Istanbul, it has been seen that it is necessary to prepare their inventories, to reveal conservation problems and to do more research on the subject.