Google places neighbourhood/suburb
The dataset covers many cities around the world.
Milan metro train station
Routes of the underground lines Purpose. The dataset shows the map of the routes of the Milan underground network.
Geohash is a public domain geocode system invented in 2008
by Gustavo Niemeyer and (similar work in 1966) G.M. Morton,
which encodes a geographic location into a short string of
letters and digits. It is a hierarchical spatial data structure
which subdivides space into buckets of grid shape, which is
one of the many applications of what is known as a Z-order
curve, and generally space-filling curves.
Geohashes offer properties like arbitrary precision and the possibility of gradually removing characters from the end of the code to reduce its size (and gradually lose precision). Geohashing guarantees that the longer a shared prefix between two geohashes is, the spatially closer they are together. The reverse of this is not guaranteed, as two points can be very close but have a short or no shared prefix.