While touring the geology of Northern Ca, we stopped to see a few extinct calderas.



The same shot from Google Earth



It may be intersting to note that I learned about these remnance of a volcanic past by simply searching Google Earth looking for signs of geologic features and making note of the GPS coordinates.
Google Earth is a cool tool for this hobby.

Here, another famous volcano as some commonly thought as "a volcano inside a volcano"--the Taal Volcano

http://en.wikipedia.org/wiki/Taal_Volcano