Rtree is a ctypes Python wrapper of libspatialindex that provides a
number of advanced spatial indexing features for the spatially curious
Python user. These features include:

- Nearest neighbor search
- Intersection search
- Multi-dimensional indexes
- Clustered indexes (store Python pickles directly with index entries)
- Bulk loading
- Deletion
- Disk serialization
- Custom storage implementation (to implement spatial indexing in ZODB,
  for example)