This is the jewel of Islamic architecture and the oldest Islamic monument that has not undergone fundamental changes. It thus provides very important testimony to the creation and formation of Islamic architecture and early Islamic decorative arts. It is also considered to be one of the most beautiful monuments in the world. The building is octagonal in form and is covered on the outside with marble and glazed tilework. The interior is decorated with marble, mosaics, plaster and wood. The great gold dome that towers over the building symbolises Jerusalem.