Kayanian dynasty in the context of "Capitals of Iran"

Bactria (/ˈbæktriə/; Bactrian: βαχλο, Bakhlo), or Bactriana, was an ancient Iranian civilization in Central Asia, located in the area south of the Oxus River (modern Amu Darya) and north of the Hindu Kush mountains, within modern-day Afghanistan, Tajikistan and Uzbekistan. Bactria was strategically located south of Sogdia and west of the Pamir Mountains. These mountain ranges acted as "walls" protecting Bactria from three sides, with the Pamir mountains to the north and the Hindu Kush to the south forming a junction, and the Karakoram range towards the east.

Called "beautiful Bactria, crowned with flags" by the Avesta, the region is considered, in the Zoroastrian faith, to be one of the "sixteen perfect Iranian lands" that the supreme deity, Ahura Mazda, had created. It was once a small and independent kingdom struggling to survive against nomadic Turanians. One of the early centres of Zoroastrianism, and capital of the legendary Kayanian dynasty, Bactria is mentioned in the Behistun Inscription of Darius the Great as one of the satrapies of the Achaemenid Empire; it was a special satrapy, ruled by a crown prince or an intended heir. Bactria was the centre of Iranian resistance against the Greek Macedonian invaders after the fall of the Achaemenid Empire in the 4th century BC, but eventually fell to Alexander the Great.

The Seven Great Houses of Iran, also known as the seven Parthian clans, were seven aristocracies of Parthian origin, who were allied with the Sasanian court. The Parthian clans all claimed ancestry from Achaemenid Persians.

The seven Great Houses of Iran had played an active role in Iranian politics since the days of the Arsacid Empire, which they continued to do under their successors, the Sasanians. Only two of the seven – the House of Suren and the House of Karen – however, are actually attested in sources date-able to the Parthian period. The seven houses claimed to have been confirmed as lords in Iran by the legendary Kayanian king Vishtaspa. "It may be that [...] members of them made up their own genealogies in order to emphasize the antiquity of their families." During Sasanian times, the seven feudal houses played a significant role at the Sasanian court. Bahram Chobin, a famed military commander of Hormizd IV (r. 579–590), was from the House of Mihran.

Kay Khosrow (Persian: کیخسرو) is a legendary king of Iran of Kayanian dynasty and a character in the Persian epic book Shahnameh. He was the son of the Iranian prince Siavash who married princess Farangis of Turan while in exile. Before Kay Khosrow was born, his father was murdered in Turan by his maternal grandfather Afrasiab. Kay Khosrow was trained as a child in the desert by Piran, the wise vizier of Afrasiab. His paternal grandfather was Kay Kāvus, the legendary Shah of Iran who chose him as his heir when he returned to Iran with his mother. The name Kay Khosrow derives from Avestan 𐬐𐬀𐬎𐬎𐬌 𐬵𐬀𐬊𐬯𐬭𐬀𐬎𐬎𐬀𐬢𐬵𐬀 Kauui Haosrauuaŋha, meaning "seer/poet who has good fame".

Vishtaspa (Avestan: 𐬬𐬌𐬱𐬙𐬁𐬯𐬞𐬀 Vištāspa; Old Persian: 𐎻𐏁𐎫𐎠𐎿𐎱 Vištāspa; Persian: گشتاسپ Guštāsp; Ancient Greek: Ὑστάσπης Hustáspēs) is the Avestan-language name of a figure appearing in Zoroastrian scripture and tradition, portrayed as an early follower of Zoroaster, and his patron, and instrumental in the diffusion of the prophet's message. Although Vishtaspa is not epigraphically attested, he is – like Zoroaster – traditionally assumed to have been a historical figure, although obscured by accretions from legend and myth.

In Zoroastrian tradition, which builds on allusions found in the Avesta, Vishtaspa is a righteous king who helped propagate and defend the faith. In the non-Zoroastrian Sistan cycle texts, Vishtaspa is a loathsome ruler of the Kayanian dynasty who intentionally sends his eldest son to a certain death. In Greco-Roman literature, Zoroaster's patron was the pseudo-anonymous author of a set of prophecies written under his name.