My UNESCO heritage site collection has been growing greatly, often from the kind assistance of random Postcrossers and their official Postcrossing cards. One recent card comes from Claudia in Ireland and shows the neolithic site of Bru na Boinne in County Meath:
The site includes huge mounds, many tombs, and henges. It predates the Egyptian pyramids, but shows knowledge of science and astronomy by its creators.
The stamp shows the Beadlet Anemone, which has nothing to do with Bru na Boinne, but is nevertheless quite interesting looking as well:
Hopefully more UNESCO cards will come my way through Postcrossing. My recent record has been quite good; I am receiving some very lovely heritage sites with surprising frequency.