Masmak Fort, Military fortress in central Riyadh, Saudi Arabia

Masmak Fort is a fortress and museum in the ad-Dirah neighborhood of Riyadh, Saudi Arabia. The building displays a square floor plan with four rounded watchtowers at the corners, a central courtyard, and walls several meters thick.

Abdullah bin Faisal commissioned the fortress in 1865 as an administrative seat and defensive installation. In January 1902, Ibn Saud captured the structure after a nighttime raid and made it the starting point for the unification of Saudi Arabia.

The name Masmak derives from al-Masmak, meaning a thick, high, fortified building, from the thickness of its side walls and floors; locals shifted the original name Mismak by turning the s to a ṣ. The gate holds a small opening called al-Khokha, narrow enough for only one person to pass bent over, a defensive feature. The majlis, facing the entrance, keeps a Najd-style hearth.

The ground-floor rooms display everyday items and tools, while the upper levels provide views over the surrounding streets. Guided tours explain the function of the different areas and the construction method using rammed earth.

A spearhead still lodges in the palm wood door at the main entrance, where it has remained since the 1902 attack. The mark shows the exact point where defenders were breached during the fight.