The Khorasani style (Persian: شیوه معماری خراسانی‎) is a style (sabk) of architecture when categorizing Iranian architecture development in history. It is the first style of architecture appearing after the Muslim conquest of Persia, but is highly influenced by pre-Islamic designs. Landmarks of this style appear in the late 7th century, and span through the end of the 10th century CE.

Examples of this style are Mosque of Nain, Tarikhaneh-i Damghan, and Jame mosque of Isfahan

Jameh Mosque of Nain
The Jāmeh Mosque of Nā’īn (Persian: مسجد جامع نایین‎ – Masjid-e-Jāmeh Nā’īn) is the grand, congregational mosque (Jāmeh) of Nā’īn city, within Isfahān Province of Iran. Although the mosque is one of the oldest in Iran, it is still in use and is protected by Iran’s Cultural Heritage Organization.

This mosque is perhaps one of the oldest mosques in Iran that although belong to hundred years ago but kept its original architecture. French professor, Arthurp Pops believed that the mosque foundation goes back to 9th century. It has a very simple plan but is still very beautiful. The mosque contains a central rectangular courtyard that is surrounded with hypostyles on three sides. At one of these hypostyles the mihrab of the mosque is located. The mihrab at Islamic mosque is a niche at wall that shows the direction of “Qebleh” that is the direction of Mecca the holy city that Muslims prays towards it five times daily. This mihrab has an amazingly beautiful stucco work decoration, created probably during the 9th or 10th century. Also right beside it, there as an altar made of wood with delicate wooden inlay work. The Mosque also has a 28-meter-high minaret belonging to the Seljuk era,10th century.

Specifications
The mosque is one of the oldest in Iran, dating back to the 9th century. The interiors however are Seljuki in brick craftsmanship, and therefore allude to the 11th century.

Like the Tarikhaneh of Damghan and the Jameh Mosque of Isfahan, this mosque is “Khorasani” in its architectural style (sabk).

Jameh Mosque of Isfahan
The Jāmeh Mosque of Isfahān or Jāme’ Mosque of Isfahān (Persian: مسجد جامع اصفهان‎ – Masjid-e-Jāmeh Isfahān) is the grand, congregational mosque (Jāmeh) of Isfahān city, within Isfahān Province, Iran. The mosque is the result of continual construction, reconstruction, additions and renovations on the site from around 771 to the end of the 20th century. The Grand Bazaar of Isfahan can be found towards the southwest wing of the mosque. It has been a UNESCO World Heritage Site since 2012.

Built during the Umayyad dynasty, it is rumored in Isfahan that one of the pillars of this Mosque were personally built by the Caliph in Damascus. Prior to it becoming a Mosque, it is said to have been a house of worship for Zoroastrians.

Specifications
This is one of the oldest mosques still standing in Iran, and it was built in the four-iwan architectural style, placing four gates face to face. An iwan is a vaulted open room. The qibla iwan on the southern side of the mosque was vaulted with muqarnas during the 13th century. Muqarnas are niche-like cells.

Construction under the Seljuqs included the addition of two brick domed chambers, for which the mosque is renowned. The south dome was built to house the mihrab in 1086–87 by Nizam al-Mulk, the famous vizier of Malik Shah, and was larger than any dome known at its time. The north dome was constructed a year later by Nizam al-Mulk’s rival Taj al-Mulk. The function of this domed chamber is uncertain. Although it was situated along the north-south axis, it was located outside the boundaries of the mosque. The dome was certainly built as a direct riposte to the earlier south dome, and successfully so, claiming its place as a masterpiece in Persian architecture for its structural clarity and geometric balance. Iwans were also added in stages under the Seljuqs, giving the mosque its current four-iwan form, a type which subsequently became prevalent in Iran and the rest of the Islamic world.

Responding to functional needs of the space, political ambition, religious developments, and changes in taste, further additions and modifications took place incorporating elements from the Mongols, Muzzafarids, Timurids and Safavids. Of note is the elaborately carved stucco mihrab commissioned in 1310 by Mongol ruler Oljaytu, located in a side prayer hall built within the western arcade. Safavid intervention was largely decorative, with the addition of muqarnas, glazed tilework, and minarets flanking the south iwan.

The cupolas and piers that form the hypostyle area between the iwans are undated and varied in style, endlessly modified with repairs, reconstructions and additions.

The origins of this mosque lie in the 8th century, but it burnt down and was rebuilt again in the 11th century during the Seljuk dynasty and went through remodeling many times. As a result, it has rooms built in different architectural styles, so now the mosque represents a condensed history of Iranian Architecture.

Source From Wikipedia