At the heart of ancient Bastam, now a village-suburb of Shahrud (around 7km from centre), is a collection of mostly 13th-century historical buildings. The main group is set around the relatively simple grave of Bayazid Bastami (804–874), a philosopher nicknamed 'Sultan of gnostics' who fused Muslim, Mithraic and Zoroastrian ideas in formulating a poetic form of Sufism. Behind, a contrastingly grand imamzadeh has an attractive, almost art nouveau, floral interior. The associated Bayazid mosque has a remarkable grey mihrab.
One block behind the complex, the 1285 Jameh Mosque backs onto the fine 1313 Borj Kashani, a circular tomb-tower which possibly doubled as an astronomical observatory, like the tower at Radkan.