Persian literature is one of the world's oldest literatures. It spans two-and-a-half millennia, though much of the pre-Islamic material has been lost. Its sources have been within Greater Iran including present-day Iran, Iraq, the Caucasus, and Turkey, as well as regions of Central Asia where the Persian language has historically been the national language. For instance, Rumi, one of Iran's best-loved poets, born in Balkh or Vakhsh (in what is now Afghanistan), wrote in Persian, and lived in Konya, then the capital of the Seljuks. The Ghaznavids conquered large territories in Central and South Asia and adopted Persian as their court language. There is thus Persian literature from Iran, Mesopotamia, Azerbaijan, the wider Caucasus, Turkey, western parts of Pakistan, Tajikistan and other parts of Central Asia. Not all this literature is written in Persian, as some consider works written by ethnic Persians in other languages, such as Greek and Arabic, to be included. At the same time, not all literature written in Persian is written by ethnic Persians or Iranians. Particularly, Turkic, Caucasian, and Indic poets and writers have also used the Persian language in the environment of Persianate cultures.