There is something unnerving yet intriguing about exploring vaults and crypts. If this seems interesting to you, visit Mangshan Tombs.
This tomb site in Lao Cheng is popular with fellow travelers, so leave a spot for it on your schedule. Don't think the sightseeing ends there, however. There are plenty more options ready for you to explore after Mangshan Tombs. Luoyang Old Town, Luoyang Museum, and Lijing Gate are not far away.