Short answers, pulled from the story.
Ahmad ibn Rusta Isfahani was a tenth-century Muslim Persian explorer and geographer whose life extended beyond the year 903 CE. He was born in Rosta, a district within the city of Isfahan during the Abbasid Caliphate.
Ibn Rusta wrote a geographical compendium titled Kitāb al-A‘lāq al-Nafīsa which translates to Book of Precious Records. The text covers non-Islamic peoples across Europe and Inner Asia including the British Isles and Anglo-Saxon England.
He described twenty districts called rostaqs containing details not found in other geographers' works. The town itself was perfectly circular with a circumference measuring half a parasang surrounded by walls defended by one hundred towers.
Professor Daniel Chwolson misspelled his name as Ibn Dasta(h) when translating the work into Russian in 1869. Consecutive editions of that translation included footnotes suggesting the Arabic original actually meant unclean or impure rather than clean.
An ancient ruler crowned within the midst of Slavs bore the title sacred king and ruled more powerfully than his deputy Zupan. His capital city Drzvab hosted a fair lasting three days every month according to the chronicle Al-Djarmi.