After the death of Jahangir, his son Shahjahan ascended to the Mughal throne. He went on expanding the kingdom to the south.In alliance with the Adilshahi kingdom, he defeated the Nizamshashi and annexed a large part of its territory to the Mughal empire. With a view to secure the north-west frontier of his empire, he tried to conquer the regions of Kandhahar, Balkh and Badakshan in central Asia. He, however, did not succeed. Shahjahan is best remembered for the perfectly proportioned Taj Mahal. He also built a palace of unbelievable splendor in Delhi. These and other buildings stand as examples of the Mughal glory. Shahjahan's reign was a troubled when his sons took his throne by force. Shahjahan was taken ill in 1657. This triggered a war on succession among his sons. In this, Aurangzeb emerged victorious. He imprisoned his ailing father Shahjahan and proclaimed himself the Emperor. Shahjahan died in 1666,while still under house arrest in Agra fort. The reign of Shahjahan is regarded as the golden period of the Mughal architecture.