Sigal was a city of the Helmund valley

Valley

In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

 in south-west Afghanistan

Afghanistan

Afghanistan , officially the Islamic Republic of Afghanistan, is a landlocked country located in the centre of Asia, forming South Asia, Central Asia and the Middle East. With a population of about 29 million, it has an area of , making it the 42nd most populous and 41st largest nation in the world...

 (ancient Sacastene).

The presence of the Sakas in Sakastan

Sakastan

Sakastan or Sakaistan or Sakasthan is a term indicating certain regions of the South Asia where the Scythians or Sakas settled around 100 BC. Sakastan region includes southern Afghanistan; Punjab, Khyber Pakhtunkhwa, and Sindh provinces of Pakistan; also includes Gujarat, Rajasthan, Haryana and...

 in the 1st century BCE, with their capital at Sigal, is mentioned by Isidore of Charax

Isidore of Charax

Isidorus Characenus , commonly translated Isidore of Charax, was a geographer of the 1st century BC/1st century AD about whom nothing is known but his name and that he wrote at least one work....

 in his "Parthian stations". He explained that they were bordered at that time by Greek cities to the east (Alexandria of the Caucasus

Alexandria of the Caucasus

Alexandria on the Caucasus was a colony of Alexander the Great...

 and Alexandria of the Arachosians), and the Parthian-controlled territory of Arachosia

Arachosia

Arachosia is the Latinized form of the Greek name of an Achaemenid and Seleucid governorate in the eastern part of their respective empires, around modern-day southern Afghanistan. The Greek term "Arachosia" corresponds to the Iranian land of Harauti which was between Kandahar in Afghanistan and...

 to the south:

"Beyond is Sacastana of the Scythian Sacae, which is also Paraetacena, 63 schoeni. There are the city of Barda and the city of Min and the city of Palacenti and the city of Sigal; in that place is the royal residence of the Sacae; and nearby is the city of Alexandria (and nearby is the city of Alexandropolis), and six villages." Parthian stations, 18.