Abu 'Ali Ahmad b. 'Umar Ibn Rusta was born in Isfahan at an unknown date and he flourished in the first decade of the 10th century CE. Only the seventh volume of his Kitab al-A'laq al-nafisa has survived. The work deals with mathematical, descriptive and human geography and a variety of historical and other subjects. One of his sources seems to have been a more complete version of Ibn Khurradadhbih, which has not survived. The Kitab al-A'laq al-nafisa, which has been characterized as an encyclopedia of geographical knowledge, is a rich source on the kinds of subjects that interested the cultivated classes of Abbasid society. It is published here together with the Kitab al-buldan ('The book of countries') by al-Ya'qubi (d. c. 905 CE). al-Ya'qubi's Kitab al-buldan is an administrative geography based in part on the author's extensive travels, which also contains valuable historical data.