Geologists would look for level places (no mountain building, faults or fissures, etc) where they might find the oldest surface rock. This would indicate little weathering. The Canadian shield satisfies these criteria--Precambrian basement rock around which much of the North American plate is wrapped. It extends from Lake Superior towards the Arctic.
The one drawback for this area are the episodic periods of glacial ice which scour it, occasionally dropping erratics. These episodes tend to be widely spaced in time.