Merge and Modify Maps
Merge maps and modify their options by using Show.
Take two maps, each containing a colored polygon.
In[1]:=

spain = GeoGraphics[{GeoStyling[Red, Opacity[0.5]],
Polygon[Entity["Country", "Spain"]]}]
Out[1]=

In[2]:=

italy = GeoGraphics[{GeoStyling[Green, Opacity[0.5]],
Polygon[Entity["Country", "Italy"]]}]
Out[2]=

Merge the maps and modify the result, in this case adding geo grid lines.
In[3]:=

Show[spain, italy, GeoGridLines -> Automatic]
Out[3]=

Modify the map further, now changing the style of the geo background.
In[4]:=

Show[spain, italy, GeoGridLines -> Automatic];
Show[%, GeoBackground -> "Satellite"]
Out[4]=
