Sadd Samallaqi is an old dam located 30 km southwest of Taif in the fertile Wadi Thumalah in Makkah Region, Saudi Arabia. It is a significant dam for its size and condition, and it is considered the largest dam in the Taif region. The dam was built traditionally with double-faced wall masonry, and its walls are made of large, rectangular stone blocks, and its upstream side is waterproofed. Close to the dam are two historical wells, connected by a canal. While its exact origins are unclear, architectural similarities with Yemeni structures suggest a possible pre-Islamic era origin, despite Early Islamic Kufic inscriptions indicating Umayyad use. Its heritage value lies in its period mix, and integration into the surrounding agricultural landscape.