The fort was built in 1535 subsequent to a defense alliance forged by Bahadur Shah, the Sultan of Gujarat and the Portuguese when Humayun, the Mughal Emperor waged war to annex this territory. The fort was strengthened over the years, till 1546.
Fort Diu, is located on the west coast of India in Diu, a Union Territory, administered by the Government of India. The fort was built by the Portuguese during their colonial rule of the Diu island. The Diu town is located to the west of the fort.
Portuguese ruled over this territory from 1537 (from the year they took control of the fort and also the Diu town fully) till 1961 (for 424 years, the longest period by any colonial rule in the world) they were forced to quit only in December 1961 (even though India became an independent country in 1947) during a military action called the "Operation Vijay" launched by the Government of India, whereafter Diu was merged with India and became a centrally administered Union Territory (UT).
The importance of the Diu Fort was highlighted by an opinion poll conducted (through the Internet and telephone when 239,418 people participated in Portugal) by the Portuguese (Portuguese government’s initiative) to list out the New Seven Wonders of Portugal built during their colonial rule. The Diu fort and the Basilica of Bom Jesus in Old Goa were chosen as the two wonders from India, among the seven from across the world, out of a list of 27 monuments built in 16 countries during the Portuguese rule.
The fort is a large and impressive structure on the coast of the Diu island. It commands a magnificent view of the sea. It skirts the sea on three sides. The outer wall of the fort was built along the coast line. The inner wall had bastions on which guns were mounted. A double moat (outer one is a tidal moat) between the outer and inner walls provided security to the fort. The moat that separates the fortifications from the castle has been cut through sandstone rocks. A jetty built then on the northwestern side is still in use. The fort was provided with three entry gates. A bastion built earlier by the Sultan in the deep water channel, next to the fort walls, was further strengthened by the Portuguese.
In the main entry gate, there are five large windows with stone galleries on the main front wall. From the fort, a glittering view of the Panikotha fort located in the sea, off the coast opposite to Diu Fort, could be seen in the evenings. There are several cannons (some of them made of bronze appear well preserved) still seen at the top of the Diu fort. Also seen are collection of iron shells scattered around in the fort area. The fort is approached from a permanent bridge. The entrance gateway to the fort has an inscription in Portuguese. The bastion at the gate is named St. George.
A large light house is also located at one end of the fort. Even now the ruins of the walls, gateways, arches, ramps, bastions of the fort provide an impressive view of the extent of military defenses that the fort provided in the past. Within the fort, well laid out gardens have paths bordered by old cannons.