Question: The Iron Gate breaks up the mountains between Samarkand and a province which is 20 kilometers northwest of what provincial capital?

Context paragraphs:
DR-5: DR-5 is of one of the main highways in the Dominican Republic.  The highway begins at a T-interchange with DR-1 in Villa Bisonó in the small town of Navarrete located about 20 kilometers northwest of Santiago de los Caballeros.  Initially DR-5 starts north of Santiago with a junction with DR-1.  DR-1 continues northwest to Monte Cristi while DR-5 turns northeast to the Cities of Puerto Plata, Sosua, and its ending point at the Samana Province.

Varvara, Chalkidiki: Varvara is a village in Chalkidiki, in Greece.  It is located in the north of Chalkidiki, built at 550 m height, between the hills Derveniko and Sougkliani.  It is part of Aristotelis municipality.  Its population is 538 residents according to 2011 census.  It is 20 kilometers northwest of Arnaia.  In the east of the village there are the Aegean coasts and the ancient city Stagira, the birthplace of Aristotelis.

Deir as-Sudan: Deir as-Sudan (Arabic: دير السودان‎ ‎ ) is a Palestinian town in the Ramallah and al-Bireh Governorate, located 20 kilometers Northwest of Ramallah in the northern West Bank.  According to the Palestinian Central Bureau of Statistics (PCBS), the town had a population of approximately 1,991 inhabitants in 2007.

Iron Gate (Central Asia): The Iron Gate is a defile between Balkh and Samarkand.  It breaks up the mountains which extend from the Hisar range south towards the Amu Darya.  In ancient times it was used as the passage between Bactria and Sogdia and was likely of great importance to any power in the region.  Its name comes from the belief that an actual gate, reinforced with Iron, stood in the defile.  It is located to west from Boysun, Surxondaryo Province.

Iron Gate Private Wine Management: Iron Gate Private Wine Management is one of the largest Canadian wine storage companies.  Iron Gate was founded by Canadian businessman and wine enthusiast Warren F. Porter.  Iron Gate operates a 100,000+ bottle subterranean cellar and helps collectors buy and sell wines at various wine auctions houses.

Helan, Mandi Bahauddin: Helan (or Helaan) is a village and union council in Phalia Tehsil, Mandi Bahauddin District, Punjab province, Pakistan.  The union council contains 10 villages (Helan, Charanwala, Burje, Kotli Qazi, Qutli, Dhingranwali, Binder Khurd, Rajoya, Saida Chak, Heger).  Helan is 20 kilometers south-east of Mandi Bahauddin, 8 kilometers north-east of Phalia, 20 kilometers south of Dinga and 4 kilometers north of Mano Chak.

Balkh: Balkh ( ; Persian/Pashto: بلخ‎ "Balkh"; Bactrian: βαχλο, "ẞaxlɔ") is a town in the Balkh Province of Afghanistan, about 20 kilometers northwest of the provincial capital, Mazar-e Sharif, and some 74 km south of the Amu Darya river.  It was historically an ancient centre of Buddhism, Islam, and Zoroastrianism and one of the major cities of Khorasan, since the latter's earliest history.

Tamsahelte: Tamsahelte (Arabic: تمساهلت) is a small village in the Zagora Province of the Drâa-Tafilalet district in southeastern Morocco, about 10 kilometers northwest of Tazzarine and 20 kilometers east of N'Kob.  It is located at around in the heart of the Ait Atta area.  The village has about five hundred inhabitants.  People live from agriculture.  Despite the dry climate, wells produce sufficient water for the residents and for irrigation of the gardens.  Tamsahelte and its region is well known for the good quality of the henna plants and dates.  The language spoken in this region is Tamazight.

Giona, Xanthi: Giona (Greek: Γκιώνα, previously known as Giouveiler ) is a settlement in the Xanthi regional unit of Greece, part of the community of Avdira.  It is located 9 kilometers northwest of Avdira, 9 kilometers northwest of Magiko, 11 kilometers northeast of Genisea, 7 kilometers west of Exochi, 4 kilometers east southeast of Pezoula, and 18.2 kilometers from Xanthi.  In 1991, the population of Giona was around 154 inhabitants.

Fuheis: Fuheis (Arabic: الفحيص‎ ‎ ) (also Fuhais) is a town in the Jordanian governorate of Balqa, just 20 kilometers northwest of Amman.  The town has 20,000 residents, and is majority Christian.

Supporting paragraphs: Iron Gate (Central Asia) Balkh
Answer: Mazar-e Sharif