The Japan Post Gazetteer is a simple hierarchical resource listing Japanese place names in the prefecture and ward in which they occur. It was mined from the Japan Post web site, from their list of postal codes. Currently, this information is used to provide place names for the FOKS dictionary, but it might be useful for other purposes.
The data is stored in a simple format, where each line is a space separated (depth, name, reading) tuple. Let's take a look at the first few lines of the file:
0 日本 にほん 1 北海道 None 2 北見市 キタミシ
The 0-level is the root node, listed as 日本 (Japan). For any other depth n, its parent is the previous node of depth (n-1).