Bolghar is the historic centre where Volga Bulgaria officially adopted Islam in 922 following the Baghdad embassy described by Ibn Fadlan; it was inscribed on the UNESCO World Heritage List in 2014. It is a major pilgrimage site regarded by Tatars as a 'Little Hajj' and preserves 14th-century monuments such as the Small Minaret and the Khan's Mausoleum. NOTE: no sahaba burial at the site is historically documented; the tradition of 'holy Bulgars' and early missionaries is a traditional/devotional identification, and the Sahaba monument erected in 2012 is a modern commemoration, not a verified grave. (Sources: UNESCO World Heritage No. 981; English Wikipedia 'Bolghar')