The Greek merchant Cosma Indicopleustes is known to have visited the areas around Vasai in the 6th century and the Chinese traveller Xuanzang later on June or July 640.

According to historian José Gerson da Cunha, during this time, Vasai and its surrounding areas appeared to have been ruled by the Chalukya dynasty of Karnataka.

[5] The Portuguese Armadas first reached the west coast of India after the discovery of the Cape route by Vasco da Gama, he landed at Calicut in 1498.

For several years after their arrival, they had been consolidating their power in north and south Konkan, in and around present-day Bombay and Goa.

In 1533, Diogo (Heytor) de Sylveira, burnt the entire sea coast from Bandora, Thana, Baçaim, to Surat.

Upon seeing such a formidable naval power, Malik Tokan made overtures of peace to Nuno da Cunha.

Even though the Portuguese were numerically insignificant, they fought with skill and valor killing off most of the enemy soldiers while losing only a handful of their own.

On 23 December 1534, the Sultan of Gujarat Bahadur Shah signed a treaty with the Portuguese and ceded Baçaim with its dependencies of Salsette, Bombaim (Bombay), Parel, Vadala, Siao (Sion), Vorli (Worli), Mazagao (Mazgaon), Thana, Bandra, Mahim, and Caranja (Uran).

[8] The Treaty of Vasai (1534) was signed by Sultan Bahadur of Gujarat and the Kingdom of Portugal on 23 December 1534, while on board the galleon São Mateus.

Based on the terms of the agreement, the Portuguese Empire gained control of the city of Vasai (Bassein), as well as its territories, islands, and seas.

In Salsette Island, the Portuguese built 9 churches: Nirmal (1557), Remedi (1557), Sandor (1566), Agashi (1568), Nandakhal (1573), Papdi (1574), Pali (1595), Manickpur (1606), Mercês (1606).

The Bassein fort which now lies in ruins was the administrative center and court of the northern province, and was subordinate only to Velha Goa in the south, the capital of the East Indies or the eastern faction of the Portuguese empire.

It caused considerable damage to the boats and houses, and thousands of coconut trees were uprooted and flattened, monsoon winds had pushed brackish seawater inland.

The roofs of three of the largest churches in Bassein city including the seminary and the chapel of the Jesuits were ripped off, making the structure almost beyond repair.

In a few months, the situation grew so precarious that parents were openly selling their children to Muslim brokers into slavery rather than starving them to death.

The pirates plundered all the churches outside of the fort walls and spared no violence and cruelty towards the people of Baçaim.

The East India Company had been coveting the relatively safe Bombay Harbour for many years, even before their trading post was affected by the Sack of Surat.

Bombaim was finally acquired by them through the royal dowry of Catherine Braganza, before that they had ventured to seize it by force in 1626 and had urged the directors of the East India Company to purchase it in 1652.

Their colonization efforts gradually divided the lands into estates or fiefs, which were granted as rewards to deserving individuals or to religious orders on a system known as foramen to whereby the grantees were bound to furnish military aid to the king of Portugal or where military service was not deemed necessary, to pay a certain rent.

[19] Portuguese administration saw frequent transfers of officers and the practice of allowing the great nobles to remain at court and administer their provinces.

[20] The community known as the "Bombay East Indians" were called Norteiros (Northern men) after the Court of the North, based in the fort.

In the 18th century, the Bassein Fort was taken over by the Maratha Empire under Peshwa Baji Rao's brother Chimaji Appa and fell in 1739 after the Battle of Vasai.

The Buildings inside the fort are in ruins, although there are enough standing walls to give a good idea of the floor plans of these structures.

Movies such as Josh starring Shah Rukh Khan, and Love Ke Liye Kuch Bhi Karega have a number of scenes from the fort.

The fort was also one of the shooting locations for the international hit song Hymn for the Weekend by British band Coldplay.

Auto rickshaws are also available, which can be hired from the western entrance to the railway station but cost more per head and are regarded as unsafe in that they are usually congested.