Yesterday evening at Cicci's Bar, someone told me that Pantelleria has several large 'rivers'. This sounded to me very unlikely, since the island has no natural sweet water sources of any kind. Clearly my limited knowledge of the Italian language had to be the reason of this misinterpretation.
Still, after some puzzlement, it became clear that they actually do exist, but only after some heavy raining like yesterday. These 'rivers' are actually huge trenches, which form certain patterns that can only be viewed from high up in the sky. Apparently these outlines already exist for hundreds of years and are used as beacons by travelling birds. If they would be altered, thousands of birds would get confused, or even get lost, during their annual crossing. Therefore, these landmarks are highly protected from any interference up to a level that in certain areas, ground works for basic utilities such as electricity and running water, are complex to conduct and as a result haven't been done yet.
The thing what also sounded remarkable to me, is the fact that birds only use these naturally formed patterns as guides, and not for instance streets or buildings.

Does anyone have some more information about this?