Many animals - humans included - are able to build sophisticated mental 'maps' of their surroundings. These 'maps' allow us to reliably (and relatively easily) navigate from location to location using highly complex routes.

It's known from patients who have had damage to the brain's hippocampus area that this structure is crucial to the storage and retrieval of these 'maps'.

In addition, a year 2000 study of London taxi drivers (who, as part of their licence were required to learn the locations and names of thousands of street names and important buildings etc.) found, via MRI scans, that their hippocampi actually grew in size as compared to control groups.(ref.)

The neurological mechanisms which the hippocampus (in conjunction with other brain areas) uses to store these complex maps are completely unknown.

It's thought that the ability to store and retrieve 'maps' is probably an 'ancient' development - given that the hippocampus is apparently a very old part of the brain (it's found in all other vertebrates), and how important it is to be able to get reliably from A to B and back.

Notes :

[1] These 'mental maps' are built from experience, rather than being innate. Other mechanisms (largely unknown) are very probably in use when animals migrate - example :The Sardine Runplugin-autotooltip__plain plugin-autotooltip_bigThe Sardine Run

"The term ‘sardine run’ is part of the cultural heritage of the South African nation and refers to a natural phenomenon that is well known to the general public but still poorly understood from an ecological perspective. This lack of understanding has stimulated numerous hypotheses, often contradictory, that try to explain why (ultimate factors) and how (proximate factors) the run occurs.

[2] The maps are often thought-of as 2D only, but can effortlessly be 3D as well - for example in high-rise urban scenarios.

Also see : Memoryplugin-autotooltip__plain plugin-autotooltip_bigMemory

inexplicable

"Although it is commonly accepted that learning and memory occur via enduring changes in neuronal properties such as synaptic strength within a network of neurons, many details of these processes remain unknown, including the mechanisms responsible for the persistence and maintenance of memory over long periods of time.