Rock fences are interesting to take a look at. They usually reflect local geology remarkably well because it is expensive to transport such a heavy material which is readily available in most places. Here I present a collection of images of rock fences and walls I have taken so far.
Unfortunately my collection is very small but this post in its current state is just a start. I plan to update it as I take new photos. Now I have a reason to hunt these walls and a place where to upload the photos.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113426498557362
Ignimbrite (welded tuff). Gran Canaria, Canary Islands, Spain.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113424034192210
Mudstone (turbidite). Cliffs of Moher, Ireland.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113420524292018
Andesite or basaltic andesite. Red blocks are weathered. Santorini, Greece.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113476261131490
Quartzite. Connemara, Ireland.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113517544186034
Basalt or basanite. La Palma, Canary Islands, Spain.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113523408248562
tuff (ignimbrite). Gran Canaria, Canary Islands, Spain.
http://picasaweb.google.com/107509377372007544953/Syenite#5830113478740527506
Quartzite. Santorini, Greece.
http://picasaweb.google.com/107509377372007544953/Tenerife#5835287153442706386
Ignimbrite. Tenerife, Canary Islands, Spain.
http://picasaweb.google.com/107509377372007544953/Tenerife#5835533261787961666
These rocks may look like man-made bricks but they have entirely natural composition. This is the same Tenerife ignimbrite shown in the previous picture.
http://picasaweb.google.com/107509377372007544953/Tenerife#5835482892065455538
Pumiceous lapillistone (pumice fall deposit known as Granadilla pumice), Tenerife, Canary Islands, Spain.
http://picasaweb.google.com/107509377372007544953/2015#6191004866314945746
Wall made of gneiss in Sweden.
It was noted in the Roadside Geology of Indiana, that if you look at foundations of buildings built before railroads and away from navigable waterways, that the foundation stone is typically local stone as well. In Europe this might also apply to older buildings.
Yes, it seems to be the case. In my home country northern part of it has limestone bedrock and southern has weakly cemented sandstone which can not be used as a building material. Limestone houses are common in the north but almost absent in the south. Although Estonia is a small country, ony few hundred kilometers from one end to another. There are old stone houses in the south but they are made of granite and gneiss (glacial drift rocks).
really great idea