Before this Hall was built, there had been, at current position, Ikaruga palace built by prince Shotoku in 601. The prince had dwelt in the palace until his death in 622. But, more than 20 years later after his death, the palace was burnt down due to political conflict in 643 and the descendants of the prince commited suicide.
About 100 years later after the terrible incident, high-ranked monk Gyoshin Souzu built here a temple called Johguh-ouin or Johguh temple in 739, as a monument to the memory of the prince. Johguh is another respected name of the prince Shotoku.
The temple is today's Eastern Precinct (Toh-in Garan) and the heart of the precinct is Hall of Visions (Yumedono) of octagonal pavillion.

Hall of Visions (National Treasure)