While surfing I found wonderful, photo realistic landscapes (see images found by Google).
As a matter of course I wanted to create such landscapes myself ;-))
Searching further, I found Terradreams where eventually I came to know about Terragen, a free scenery generator.
I played around with the program and every time I created a ‘postcard’ I felt like being on holidays ;-)
Links:
Terragen: A free scenery generator
Terradreams: A website dedicated to Terragen with forums, tutorials, links to plug-ins and so on