High Quality Content by WIKIPEDIA articles! Over-the-Rhine, sometimes shortened to OTR, is a neighborhood in Cincinnati, Ohio. It is believed to be the largest, most intact urban historic district in the United States. Over-the-Rhine was added to the National Register of Historic Places on May 17, 1983 with 943 contributing buildings. Besides being a historic district the neighborhood's arts scene is unparalleled in size and caliber within Cincinnati.