The areas is almost all highlands. It is bounded west by the crests of the Zagros Mountains. The northern limit is set by the Lesser Caucasus ranges, excepting a triangle poking beyond them into the Trans-Caucasian lowlands. The east is marked off by the Talish(3) peaks, an extension of the Elburz(4). The south zig zags through mountains and plateaus. Salty Lake Urmia(5) sits high in the northwest, Asia's sixth or seventh largest lake. Mount Sabalan near where the Lesser Caucasus meet the Talish is the only peak to top 4000 meters.
The majority probably speak Azeri(6), the national language of nearby Azerbaijan(7). Perhaps one in three speak Kurdish, living in Kurdistan and west of Lake Urmia. Perhaps one in twenty to one in ten, living further east among the Azeri, speak Gurani; they regard themselves as Kurds.
Almost everyone is a Moslem, mostly Shi'ite although a substantial minority of Kurds are Sunni.
There is one city with a metropolitan area exceeding one million, Tabriz. Despite its having been the capital of empires, its monuments, like the Blue Mosque, are in ruins, victims of earthquakes, the most recent severe one in the 1940's.
People have been there for as long as they have anywhere else in mainland sub-Arcti Asia--perhaps nearly 100,000 years. Speakers of Proto-Iranian probably lived in the area 3,000 years ago. The Medes, speaker of a lost Iranian language, lived in this area--as evidenced by toponyms--in the middle of the first millenium B.C.E. In Kurdistan around the same time there were speakers of Old Persian; their descendents now live further southeast. In the fourth century B.C.E. the Persian kingdom of Atropane(8) was founded where Azeris now live; it was after this kingdom that the Azeri language and land are named. Azeri speakers however came much later. Their ancesters arrived from the north between the seventh and 11th centuries, and spoke the language that fathered Turkmen, Azeri and Turkish. Two other languages were of former importance because they were used by political and economic elites: Aramaic starting about 2500 years ago, and Armenian in the northwest when Tabriz was that nation's capital.
The series of religions was similar to Persia as a whole. I. Practices derived from Indo-European roots. II. Zoroastrianism, introduced from the north, and eventually becoming a state religion. III. Alongside this official religion developed Christianity, and syncretic blends of Christianity and Zoroastrianism. IV. Islam took the area by conquest in the middle of the first millenium C.E. and largely exterminated the older religions. I'm not sure how the area became Shi'ite: whether in the original schism or later. I presume the Azeri began as Suuni Moslems since their relatives, the Turkmen, still are; they became Shi'ite early.
west from the northwest
north
east of Azerbaijan Sharqi, northeast of Zanjin and north, east and south of Qazvin
south of Kurdistan and Zanjan provinces, and southwest of Qazvin Province
west of southern Azerbaijan Gharbi, and of Kurdistan Provinces
(1) Azarbayane-e in Persian.
(2) Kordestan in Persian.
(3) Tavalesh in Persian.
(4) Alborz in Persian.
(5) Orumiyeh in Persian.
(6) Not to be confused with the local but unrelated language of Azari.
(7) Azarbaycan in Azeri.
(8) Its Greek name.