In 1598, Shah Abbas, the 5th Safavid Shah or king of Iran, decided to shift the capital of his Persian empire from the northwestern city of Qazvin to the central city of Isfahan or Esfahan to distance his capital from any future assaults by Iran's neighboring arch-rival, the Ottomans, and to gain more control over the Persian Gulf.

During that time, he took a mammoth plan to remake the city to commemorate its new role. At the same time, to create a place to hold national events, Naqsh-e Jahan Square was designed. However, the crown of the project was Masjid-i Shah or Shah Mosque, which would replace the old Jameh Mosque for conducting the Friday prayers.

Located at the heart of the city of Isfahan, and built between 1611 and 1629 as a part of Naqsh-e Jahan square complex, the Imam Mosque or Masjid-i Imam, formerly known as Masjid-i Shah or Shah Mosque, is regarded as the most important display of Persian architecture in the Islamic era. Commissioned under the rule of the Safavid King Shah Abbas and considered one of the most important historical Mosques in Isfahan, it is a timeless masterpiece in terms of architectural beauty, and aesthetic workmanship in tiling. Despite his ardent desire to complete the construction of the mosque before his death, Shah Abbas died a few months before the completion of the majestic building of the mosque with the biggest dome on the city.

There is one strange and prominent feature of the Imam Mosque, completed around 1630 during the rule of Shah Safi, the successor of Shah Abbas. Unlike most of the important buildings which face toward Mecca, the entrance of the Imam Mosque leads another way. However, after taking entry through the gate, a slight turn on the right side changes the direction, and one reaches the yard of the mosque, facing exactly to the direction of the holy city of Mecca.

This subtle and crafty move also created the wonder to make the entrance and the main dome of the mosque equally visible from the square, without blocking the view of each other. The other unique architectural feature of the mosque is its acoustic properties. Anything spoken under the dome will be clearly heard by anyone inside the mosque.

The Imam Mosque consists of two separate structures of a spectacular gate of entry with two minarets and the main building of the mosque crowned with a big dome and also adorned with minarets. The mosque yard lies between them. The semicircular gateway of the Imam Mosque, measuring around 89 feet (27 m) in height, resembles a recessed half-moon, framed by turquoise ornament and decorated with rich tile-work called muqarnas, the traditional form of Islamic architecture, ritually used in Islamic buildings. The ornamental entrance is flanked by two tall minarets with a height of 138 feet (42 m), topped by beautifully carved, wooden balconies with muqarnas running down the sides. The entrance portal of the mosque is aesthetically executed in tile mosaic in a full palette of seven colours that included dark Persian and light Turkish blue, black, green, light brown, and yellow. Apart from that, the dark blue ground frames the gateway contains a wide inscription band with religious texts written in white thuluth script, used in medieval times on mosque decorations.

Facing northwards, the mosque's portal to the Square is usually under the shadow, but since it has been coated with radiant tile mosaics, it glitters with a predominantly blue light of extraordinary intensity. Except in the covered halls of the building, which were later changed to tiles of cooler, yellowy-green shades, the tiles in the Masjed-e Shah are predominantly blue. The huge Masjid-e Shah measuring 330 feet by 430 feet (100 by 130 m), said to contain 18 million bricks and 475,000 tiles, and used the new haft rangi, or seven colour style of mosaic.

Inside the entrance, there is a large marble basin set on a pedestal, which no longer serves to provide water to the worshipers. However, the entrance leads to the main courtyard, centered around a large pool. A ten feet tall and three feet wide large marble tablet on the southwestern wall, known as the mihrab, indicating the direction of Mecca, has a gold-encrusted cupboard on its top. It is said that the cupboard contains two important relics. One of them is a Quran, said to have been copied by Imam Reza, a descendant of the Islamic prophet Muhammad, and the eighth Shia Imam, while the other one is the bloodstained robe of Imam Hussain, a grandson of Muhammad, who was killed and beheaded in the Battle of Karbala on 10 October 680.

Built as a double-shelled dome, with 46 feet (14 m) spanning between the two layers, and resting on an octagonal dome chamber, the dome of the Masjid-e Shah, reaching 174 feet (53 m) in height, was the tallest in the city when it was finished in 1629. Reflecting the light of the sun, the dome covered with colourful tiles, appears like a glittering turquoise gem and could be seen from miles away. Facing northwards, the mosque's portal to the Square is usually under the shadow, but since it has been coated with radiant tile mosaics, it glitters with the predominantly blue light of extraordinary intensity.

The Imam Mosque or Masjid-i Imam, formerly known as Masjid-i Shah, is enlisted in UNESCO World Heritage Site, along with Naqsh-e Jahan Square, and is a popular destination for tourists visiting Isfahan.