Noone knows the natural spaces of Spain like a professional land surveyor! Nevertheless, if you wanna see how others have it mapped, take a look at Ourense en Verde [via GMapsMania]
Ourense en Verde is using the Google Maps API to map the natural beauty of the Ourense region in Galicia, Spain.
The map uses a nice polygon masking effect to highlight the Ourense region on the map. If you want to use the effect in your own Google Maps then you can use the Masked Polygons library from Swiss Trains. I also really like the mouse-over effect on this map's markers. When you mouse-over the green markers on the map they expand to show the name of the region marked.
Radio buttons positioned below the map allow the user to filter the results shown on the map by category, including Protected Areas for Birds, Natural Monuments and Nature Parks.