|Memory is relative spatiality. The memory is remembered through index such as special object or place which has been left strongly. These days, the indexes of the city arise and disappear more quickly than before. When I went to my hometown which I lived in my 15 years ago, that has been changed so much that it was really hard to recognize the memorial place in my childhood. My playground is gone. This project suggests the digital column such as the system of coordinates. The X and Y position of the columns are fixed. Even if the structure of the city is changed, the columns can be index which address the memory of the city. For example, the columns in the area, Avenue Y and W street under construction of a new Unified School can accumulate the memory of the place from the construction to school event around there in the future.