Seismograph introduction: There are armillary spheres and seismographs on the left and right sides of the two pavilions. They are fed by heaven and earth, and the armillary sphere and earth move in response to each other from a distance. The full name of the seismograph is Houfeng Seismograph. It is a masterpiece handed down from generation to generation by Han Dynasty scientist Zhang Heng. It was the world's first seismograph invented in the first year of Yangjia (AD 132).