Abraham ben Jacob, better known under his Arabic name of Ibrâhîm ibn Ya`qûb (al-Tartushi [often like this instead of 'al-Ṭurṭûshî']) was a 10th-century Hispano-Arabic, Sephardi Jewish (written and oral history, as well as his writings indicate his Jewish background,) traveller, probably a merchant, whose brief may have included diplomacy and espionage. His family hailed from Moorish-ruled Ṭurṭūšah close to the mouth of the Ebro: he himself may also have lived in Cordova. In 961–62 he travelled in Western and Central Europe and in Italy at least as far as Rome, where he was received in audience by the Holy Roman EmperorOtto I during the first week of February; nothing is known about his return to 'al-Andalus' (the Muslim-ruled part of the Iberian Peninsula), nor of any other travel. The memoirs and commentaries of his journey, possibly first presented to the Cordovan caliphAl-Hakam II (961–76), have been lost; only excerpts by later authors have been preserved, i.e., in Abu Abdullah al-Bakri's Book of Highways and of Kingdoms. His work is widely known as the first reliable description of the Polish state under Mieszko I, the first historical ruler of Poland. He is also noted for his description of the Vikings living in Hedeby, of the Nakonid fortification at "Dorf Mecklenburg" and of what was, in all likelihood, the nucleus of the later ducal castle and palace at Schwerin. Ibrahim ibn Yaqub has a unique place in Czech history as the first person to mention the city of Prague in writing.