The building is also known as the Ash Sharqiya Fort. It was built by the Portuguese under Philip I of Portugal in the 1580s to protect the harbor after Muscat had twice been sacked by Ottoman forces. It fell to Omani forces in 1650. During the civil wars between 1718 and 1747, the fort was twice captured by Persians. The fort was extensively rebuilt later. For much of the 20th century it was used as Oman’s main prison, but this function ended in the 1970s.
The fort consists of two towers connected by a wall punctuated by holes for cannons. The building is completely isolated and cannot be accessed from its rocky façade. There is a small bridge and stairway ending at one of the holdouts for safe exit.
Fort Al-Jalali was restored in 1983 and converted into a private museum of Omani cultural history that is accessible only to dignitaries visiting the country. Exhibits include cannons, old muskets and matchlocks, maps, rugs and other artifacts.