While most of the major forts in Rajasthan were built on hilltops, the massive Junagarh Fort was built amidst the Thar Desert and the new city of Bikaner gradually grew up around it. The magnificent structure, considered to be one of the top attractions of the city, was built in 1594 by Raja Rai Singh, the sixth ruler of Bikaner. Initially named Chintamani, Junagarh Fort earned its present name much later, in the early 20th century, when the ruling family moved out and shifted to the Lalgarh Palace, located outside the fort complex.

Covering a sprawling area of 5.28 hectares (52,800 sq m), the fort was built outside the original fort of the city, some remnants of which are still preserved near the Har Mandir, also known as the Lakshmi Narayan Temple. Surrounded by a wall,  3,234 feet (986 m) long, with 37 bastions and complete with a moat, the fort complex is studded with several palaces, pavilions and temples, depicting a synthesized culture, manifest in the mix of architectural styles.

Before the construction of the Junagarh Fort, there existed an old fort in the area, built in 1478 by Rao Bika, who also established the City of Bikaner, named after him. Rao Bika, who conquered the large arid lands in the northern region of Rajasthan to set up his domain, was the second son of Rao Jodha Rathore, the founder of Jodhpur City. Rao Bika knew that as the second son of Jodha Rathore, he had no chance to inherit his father’s territory or his Maharaja title, so he built his own kingdom in Bikaner, named after his father, earlier known as Jungladesh. Although a part of the great Thar Desert, Bikaner was considered in those days an oasis on the trade route between Central Asia and Gujrat coast for its adequate spring water sources.

However, Bikaner flourished under Raja Rai Singh, the sixth ruler of Bikaner, who ruled from 1571 to 1611 and accepted the dominion of the Mughals and held a high position of an army general in the court of Emperor Akbar and also his son Emperor Jahangir, along with the gift of Jagirs. With the huge increase in earnings as revenue from his Jagirs, Rai Singh decided to start his dream project, the construction of the Junagarh fort, on an almost plain land, with an average height of 760 feet (230 m). While the construction of the proposed fort began after completing the ritual ceremony on 17 February 1589, the fort was completed within five years, on 17 January 1594.

One of the main features of the massive Junagarh Fort, often described as an epitome of architectural excellence, is the stone carvings done in red and gold sandstone. However, as its architecture reflects several types of architectural styles, it can be called a true depiction of composite culture.

While the earliest works clearly depict Rajput architectural style, reflecting the influence of Mughal architecture, the second type depicts semi-western architecture reflecting British influence and finally the revivalists Rajput architecture that evolved particularly during the rule of Maharaja Ganga Singh, who ruled from 1887 to 1943 and built the Ganga Niwas Palace in the fort complex.

All the seven gates of the Junagarh Fort, locally known as Pols, are made of red sandstone, except the two east facing main gates, namely Karan Pol and Suraj Pol, which are built of yellow sandstone, signifying the rays of the rising sun falling on them, which is considered as a good omen. Although earlier the Karan Pol was used as the main entrance, today the Suraj Pol is serving the purpose. While both the gates were studded with iron spikes to prevent battering of the gate by elephants of any possible invader, the Suraj Pol is flanked by two red stone statues of elephants with mahouts, their trainers, standing as the sentinels. Other gates of the fort include the Chand Pol, a double gate, Fateh Pol, Tripolia Pol and the Daulat Pol, containing forty one red handprints of the wives of the Maharajas of Bikaner, who committed Sati or self-immolation on the funeral pyres of their husbands.

The Junagarh Fort contains several marvellous palaces, complete with courtyards, balconies and aesthetic interior decorations. Among the palaces, Phool Mahal, built by Rai Singh, decorated with flower vases, rose water sprinklers and motifs, along with its walls embellished with glass and stucco works, is considered as the oldest part of the fort. Nevertheless, Karan Mahal, built by Karan Singh in 1680, to commemorate his victory against the invading Mughal Emperor Aurangzeb and to serve the purpose of the Public Audience Hall, consisting of beautiful gardens, carved balconies and glass windows, is considered one of the most exquisite palaces in the fort. Later, the palace was further embellished with Polychrome glass and patterns of mirrors by Surat Singh and Anup Singh, who also painted the palace with red and golden colour. Considered one of the grandest construction in the fort complex, the multi-storey structure of Anup Mahal, decorated with ornate wooden ceilings with inlaid mirrors, Italian tiles and fine lattice windows and balconies, along with gold leaf paintings on the walls, was built by Anup Singh, who ruled from 1669-1698.

Chandra Mahal, one of the most luxurious palaces of the Junagarh, built by Gaj Singh, who reigned from 1746 to 1787, contains gold plated deities and paintings studded with precious stones. Apart from that, it has aligned mirrors in the bedroom of the king, so that he could keep watch about any unwanted intruder. Ganga Mahal, built by Ganga Singh who reigned from 1887 to 1943, contains a large Durbar Hall, which has been transformed into a museum, known as the Ganga Singh Hall, displaying war weaponry of the Rajputs in those days, along with an aeroplane used during the First World War. Badal Mahal, an extension of Anup Mahal, displays several paintings of Shekhawati Dundlod Chiefs, depicting the King of Bikaner in different types of turbans. It also contains paintings to depict the devotion and endurance of the people for faith, displayed by standing on saws, nails and even on swords. The walls in the palace are decorated with frescoes, depicting the Hindu god Krishna and his consort Radha sitting amidst the mass of rain clouds.

The Junagarh Fort complex contains Har Mandir, a temple marked exclusively for the royal family for worshipping the Hindu deities Lakshmi Narayan, the combination of Lord Vishnu and his wife Lakshmi. Apart from celebrating the Hindu festivals of Gangaur and also Dussera, when weapons and horses were worshipped, birthdays and marriage functions of the royal family were also celebrated in the temple. There is another beautiful marble temple, located very near to the Junagarh Fort, known as Ratan Behari Temple, containing the idols of the Hindu god Lord Krishna, which was built in 1846 in Indo-Mughal architectural style, by Maharaja Narendra Ratan Singh, the 18th Maharaja of Bikaner.