Aslan's How was a hilly mound of earth that covered what had once been the Stone Table to the south of the town of Beruna in the Kingdom of Narnia, built during the Dark Age. It was also the place where Aslan was sacrificing his own life to the White Witch so that Edmund wouldn't get killed by Jadis.
Originally, the hill itself was called Aslan's Camp, which Aslan's Army used as their campgrounds and headquarters during the White Witch's reign. The hill was attacked by the Witch's Secret Police, but was successfully defended.
A thousand years after the Stone Table split in half, the Narnians erected a mound over the Table, with some hollowed-out tunnels, thus allowing it to be used as a centre of command for the Old-Narnian Army later on.