Chavín de Huántar is one of the most significant archaeological sites in Peru and the ceremonial centre of the Chavín culture, which flourished here roughly 1000–200 BC. The site is a UNESCO World Heritage Site, and the main attraction is the network of underground galleries beneath the ceremonial platform — a labyrinth of stone corridors that were used for ritual purposes, including the inhalation of hallucinogenic cactus preparations.
The bus journey from Huaraz takes three to four hours through spectacular mountain scenery, crossing the Cordillera Negra via the Kahuish Pass at over 4,500 metres. The on-site museum holds carved stone heads (cabezas clavas) that once studded the exterior walls of the main temple. Visit the site first while you have energy, then the museum. Allow a full day for the excursion, and consider joining an organised tour — local guides can explain the symbolism and history in much more detail than the signage alone.