Fort al-Jalali or Ash Sharqiyah Fort is comprised of two towers, connected by a wall with gun ports. It was built be the Portuguese in the 1580s on the foundations of an earlier fortress. It was reportedly built after successive attacks by Ottoman forces in the mid to late sixteenth century. While Muscat was largely under Portuguese control during this period, the Ottomans intermittently gained power and in the early seventeenth century, the English and Dutch began to enter the fray to gain control of the protected harbor. In 1622, a Persian-English Force took Hormuz forcing the Portuguese to fortify Fort al-Jalali to rebuff a potential attack. In 1649, under the forms of Sultan bin Saif, Omani forces wrested power over Muscat from the Portuguese. In the eighteenth century, Fort al-Jalali would be damaged in civil disputes over the Imamate as well as in advancements by Persian forces in 1738 and 1743.

In 1749, Fort al-Jalali along with Fort al-Mirani came under control of Ahmad bin Said al-Busaidi, the first ruler of the Al Said dynasty which continues to rule the Sultanate of Oman. In the mid to late eighteenth century, additions were added and al-Jalali became a military base. Following a revolt, Ahmad bin Said al-Busaidi imprisoned his son in Fort al-Jalali, foretelling its later use as a prison for into the twentieth century, holding around 200 prisoners, many of whom were captured during the Jebel Akhdar War (1954-59) or Dhofar Rebellion (1962-76).

The fort was restored in 1983 and is now a museum.