In June 2012 I was able to visit Rue de la Harpe and take some pictures of the area, to better show the history of the area and of whatever truth there was behind the Sweeney Todd/cannibal wigmaker story.
The view of Rue de la Harpe, from across the Boulevard St. Germain. Note the location of the Supermarket: the building to the right is newer and sits at a different angle, but the building behind the Supermarket is older and still follows the original trajectory of the street.
Crossroads of Rue de la Harpe and Rue St. Severin.
View from the Rue de la Harpe, looking toward Boulevard St. Germain.
Present day view from the end of Rue de la Harpe looking across Boulevard St. Germain: the brick building is the ruins of the Thermes de Cluny.
Present day view looking out towards what would have been the original trajectory of the street.
View of the ruins from the probable location of at least one of the two demolished houses (whether it would have really belonged to a baker and a wigmaker we don't know.)