Mount Moriah is the mount on which Abraham offered Isaac in Genesis 22. In 1 Chronicles 21 it is identified as the location of Arunah (or, Ornan) the Jebusite threshing floor that David bought for 600 shekels of gold. This purchase is an important fact since it demonstrates that the Jews received this area through a legal transaction. They have never sold the rights to Mount Moriah.

King David said to Ornan, “No, but I will buy them for the full price. I will not take for the Lord what is yours, nor offer burnt offerings that cost me nothing.” So David paid Ornan 600 shekels of gold by weight for the site. And David built there an altar to the Lord and presented burnt offerings. - 1 Chronicles 21:24, 25

Mount Moriah is where Solomon built his Temple.

Then Solomon began to build the house of the Lord in Jerusalem on Mount Moriah, where the Lord had appeared to David his father, at the place that David had appointed on the threshing floor of Ornan the Jebusite. - 2 Chronicles 3:1

Mount Moriah is a ridge of rock that rises from the junction point of the Hinnom and Kidron valleys. It rises through the City of David and reaches its highest elevation just northeast of the Damascus Gate in the Old City. The Temple Mount today covers about 45 acres and is built around the outcropping of the bedrock under the Dome of the Rock. It is about 118 feet lower than the highest point of Mount Moriah.