The oldest surviving mosque in Indonesia is the Great Mosque of Demak which is the royal mosque of the Sultanate of Demak, although this is not the oldest Islamic structure. The oldest Islamic structure in Indonesia are parts of the royal palace in Sultanate of Cirebon, Cirebon. The palace complex contains a chronogram which can be read as the Saka equivalent of 1454 CE. Early Islamic palaces retain many features of pre-Islamic architecture which is apparent in the gates or drum towers. The Kasepuhan Palace was probably begun in the late pre-Islamic period, and continued to grow during the Hinduism-to-Islam transitional period. The complex contains clues to the stages of the process of the gradual changes as Islam become incorporated into Indonesian architecture. Two of the Hindu features adopted into Islam in the Palace is the two types of gateways - the split portal ("candi bentar") which provides access to the public audience pavilion and the lintel gate ("paduraksa") which leads to the front court.