Zhang Heng (78–139 CE) was one of the most versatile intellects of the Han dynasty: a mathematician, astronomer, poet, inventor, and government official who in the course of a single career produced the first mechanical representation of the celestial sphere, refined calculations of pi, wrote poetry that became models of the Han literary style, and invented the world's first seismoscope. His tomb lies on the outskirts of Nanyang, and the adjacent museum documents his contributions in each of these fields.
The museum is modest in size but well-organised, with models of his inventions and an explanation of how the seismoscope worked. The tomb itself is a simple mound in a walled enclosure; visiting it requires a certain willingness to imagine the significance behind the plain exterior. Entry is free. The site is about 10 kilometres northeast of the city centre; taxis are the most practical way to reach it.