The pyramid at Saqqara, specifically the Step Pyramid of Djoser, is different from the pyramids at Giza in the following ways:
- It is a step pyramid.
Therefore, the correct answer is: It is a step pyramid.
To clarify the other options:
- The Step Pyramid is not larger than the pyramids at Giza.
- It was built earlier than the pyramids at Giza, not later.
- It was indeed built during the Old Kingdom, but this is not a distinguishing feature when comparing it solely to the pyramids at Giza, as those were also built during the Old Kingdom.