Complex sentence: The granite block foundation of the roundhouse was only covered over to make the parking lot; in early 2012, engineers found it using ground penetrating radar while examining the site in preparation for a new parking garage.
Split into simpler sentences: The granite block foundation of the roundhouse was covered over to make the parking lot rather than fully removed. In early 2012, engineers found it using ground penetrating radar while examining the site in preparation for a new parking garage.