The following is taken from Islamtoday.Com:
Question: In many sites we read about places that are alien to us. These places are very important, because they are connected with great personalities of Islam. Please give us, for the benefit of the present generation of Muslims, the exact present location of these places… 1. Bukhara for Imam al-Bukhari 2. Nasarabad and Nisapoor for Imam Muslim 3. Sijistan, Khurasan 4. Tirmidh, Transsaxonia 5. Qazwin for Ibn Majah 6. Naynawa for Imam Nawawi.
Answered by the Fatwa Department Research Committee – chaired by Sheikh `Abd al-Wahhâb al-Turayrî
These cities are described in Al-Munjid fi al-`Alâm as well as Ma`âjim al-Buldân by al-Hamawî. Below is a brief summery of what is mentioned in these works and you may refer to these books for more information.
Bukhâra: A city in the Republic of Uzbekistan, a major Islamic center which was famous during the third century AH for its scholars, mosques, and Islamic culture . Economically, it was a famous oasis in the Zarafishan valley renowned as a producer of carpets and silks.
Nasrabad: An old city in Iran. The main city in the region is known as Sijistan.
Naysabûr: An Iranian city to the west of Mashhad. It was the old capital of Khurasan, one of the main Islamic cultural centers during the middle ages, together with Balkh, Harat and Marv. Sultan Nizâm al-Mulk established a prestigious school there named al-Nizâmiyyah . The city was sacked by the Mongols and suffered several earthquakes.
Sijistan: An old area in Iran and Afghanistan. Its chief city was Nasrabad.
Khurasan: An old area in Central Asia, located to the south and west of the Amodriya valley. Some of its important cities were: Naysabur, Harat, Balkh & Marv. In this region, the Abbasid dynasty was founded and one of its famous leaders was Abû Muslim al-Khurasanî. This area is now divided between Iran, Afghanistan and Turkmenistan.
Today, the name of Khurasan is given to a province to the east of Iran on the Turkmen and Afghan borders. The provincial capital is now Mashhad. Its old capital was Naysabûr.
Tirmidh: A city in Uzbekistan in the Amodriya valley near Afghanistan’s border. It is a rich oasis watered by Sarkhan darba. It was invaded by Mûsâ b. `Abd Allah b. Khazim around 60 AH who ruled it for some time. Then it was returned to Umayyad rule by `Uthmân b. Mas`ûd in 70 AH.
Transoxiana (Mâ Warâ al-Nahr): Arabs gave this name to all the countries located to the north of the Oxus river in Turkistan. It was one of the important Islamic cultural centers. Important cities therein are: Bukharâ, Samarqand, Khayyûn, and Tashkent.
Qazwîn: An Iranian city located south of the Caspian sea. It is an inporant agricultural region and it boasts some beautiful mosques from the Seljuk era. It was the capitol for the Safavid dynasty during the eighth century AH.
Naynawa: One of the capitals of the Ashur dynasty, beside Mosul, in Iraq. It was developed in the era of Ashur rule. Now, it is an Iraqi province having eight districts with its provincial capital in Mosul. The famous scholar al-Nawawî did not come from this city, but from Nawâ, south of Damascus, Syria.