In so far as the history of Baghdad itself is concerned, the first period of course only starts with the date of the foundation of the Round City by the Caliph Mansur, closing with the death of Mamun, as Kasready said, or in other words, the period begins with the reign of the grandfather of Harun-ar-Rashid, and ends with the life of the second of his sons who attained the Caliphate. For this first period the authors have unfortunately no written contemporary authorities, but for the topography of Baghdad an event of much importance is the first siege of the capital. The Princess Zubaydah, widow of Harun-ar-Rashid, is driven out of her palace in the fief near the Katrabbul Gate, and joined her son in the Round City, which, with the Khuld Palace and the suburbs to the south along the river bank, became the last refuge of Amin and the Kasrison.