This bastion is the oldest surviving construction in the Galle Fort. It was originally built by the Portuguese as a fortress in the 16th century and was called Fortress in the 16th Century and was called Fortaleza or Santa Cruz. It was developed further by the Dutch after 1640 and was re-named Zward Bastion out of all the bastions in Galle Fort this was the one which was most heavily armed and guarded. The chief military aide serving under the Dutch commander of the Galle Commandment was in charge of this bastion. Comprising two terraces workshops for blacksmiths were located on the upper terrace while an underground powder magazine was constructed beneath the terrace.
Because the buildings were constantly covered by black smoke emanating from cannon five and the burning coal in the workshops.
It was also called the Black Fort.it is also believed that the name way derive from the African workers who worked here.
The lower terrace was called the water pas. There is a sloping tunnel, linking the upper terrace with the lower terrace.