They were Round Top and Little Round Top.

In the mists and vapors and at the distance the two hills looked like ancient towers.
Harry and George gazed at them, and then their eyes turned to the town.
It was a neat little place, with many roads radiating from it as if it were the hub of a wheel, and the thrifty farmers of that region had made it a center for their schools.
Harry had learned from Jackson, and again from Lee, always to note well the ground wherever he might ride.

Such knowledge in battle was invaluable, and his eyes dwelled long on Gettysburg.
He saw running south of the town a long high ridge, curving at the east and crowned with a cemetery, because of which the people of Gettysburg called it Cemetery Ridge or Hill.

Opposed to it, some distance away and running westward, was another but lower ridge that they called Seminary Ridge.

Beyond Seminary Ridge were other and yet lower ridges, between two of which flowed a brook called Willoughby Run.