The car was parked in/at the same place.
Which preposition should be used?
Either. It depends.
If you are referring to an actual parking place (as in a car park, with lines painted on the ground), then it would be 'in the same place'. Similarly, if you are referring to a particular spot in a street when a car has again parked 'in the same place'.
'at' would be used if you were referring more to the general site where it was parked - e.g. near a particular store, at a picnic ground.
'That's the second time I've seen that new car parked at the Jones' place. Have they got friends visiting, or have they bought a new car?