Conversation so far:
When was Erich Ludendorff with Hindenburg?
Falkenhayn was replaced as Chief of the General Staff by Field Marshal Hindenburg on 29 August 1916.
Ludendorff was his chief of staff as first Quartermaster.
Are there any other interesting aspects about this article?
They toured the Western Front meeting --and evaluating-- commanders, learning about their problems and soliciting their opinions.
What rank was he during this time?
CANNOTANSWER.

Question: What was their location?
Self-contained rewrite: What was the location of Erich Ludendorff's tour?