Alexander the Great is mentioned in the Quran as "Dhul-Qarnayn". He was a powerful king who had much influence over much of the world at the time. The Quran tells the story of how Dhul-Qarnayn traveled far and wide, meeting different people and encountering various challenges.
One of Dhul-Qarnayn's journeys took him to the edge of the world where he saw the sun setting in a murky (muddy) spring. This was a strange sight to him, so he continued on his journey until he reached a place where the sun rises every day. He then built a barrier between the two points to prevent harmful people from crossing and causing destruction.
Another journey took Dhul-Qarnayn to a tribe who complained of a tribe who were causing them harm. He decided to help by building a wall of iron between the two groups to prevent further conflict.
The Quran mentions Dhul-Qarnayn as a sign of God's power and the importance of using strength and wisdom in dealings with others.