One of the great things about Shadow World is the ability to create or explore fantastic structures, ruins and lost cities. With over 100,000 years of history there has been hundreds or thousands of interesting cultures that have risen and fallen. Sometimes real sites on Earth can spur the imagination: one of my favorites is the "Plain of Jars" in Laos.
https://en.wikipedia.org/wiki/Plain_of_Jars
and Nan Madol in Micronesia
https://en.wikipedia.org/wiki/Nan_Madol
Any others come to mind?