Dom �ber Einer Stadt (Cathedral Towering over a Town) and Medieval Town by Water by Karl Friedrich Schinkel, around 1830, originals were destroyed by fire.

http://www.pinakothek.de/karl-friedrich-schinkel/dom-ueber-einer-stadt 

you'll like this
http://vimeo.com/7809605 

http://quiteizzy.deviantart.com/art/Bebok-384567266 

 

http://fc06.deviantart.net/fs71/f/2013/082/7/b/prawn_soldier_textured_by_stillenacht-d5yy55j.jpg 

Fooking prawns 

Prawns 4 life 

http://explodingactresses.tumblr.com/ 

http://www.goodtextures.com/ looks like a very nice source for free textures. 

Complete with an underground palace and churches.

http://whc.unesco.org/pg.cfm?cid=31&l=en&id_site=32&gallery=1&&index=13

Tenth one of twentyfour is my favourite. I was close to make an speedmap similar to that on Sm173 

Licking the walls was disallowed though... 

do it anyway 

For once I can say "I've been there" too. Funnily enough all I could think about whilst I was in there was "This is really Quakey". 

How about this?

http://www.flickriver.com/photos/tags/castelo+andrade/interesting/
http://www.flickriver.com/photos/tags/monasteriodecarboeiro/interesting/
http://www.flickriver.com/photos/tags/mosteiro+monfero/interesting/

This one is man-made, by Romans, to extract gold.
http://www.flickriver.com/photos/tags/montefurado/interesting/

This is some sort of big educational park two rich brothers made 120 years ago for every one, filled with caves and strange things. Use the second link for more photos.
http://www.flickriver.com/photos/tags/parque+pasatempo/interesting/
https://www.google.es/search?q=parque+do+pasatempo&client=firefox-a&rls=org.mozilla:es-ES:official&source=lnms&tbm=isch&sa=X&ei=TAZ5UuPkC6m70QXT-ICQDQ&ved=0CAkQ_AUoAQ&biw=1920&bih=951

Those are the only ones i could think right now that aren't famous enough, but can be interesting in photos. Sorry, but they are in Galician, not in English. 

Love those caves. 

He's done concept work for Guildwars...
http://theoprins.blogspot.be/ 

http://www.boredpanda.com/abandoned-places/ 

http://translate.google.es/translate?hl=en&sl=es&u=http://lugares-con-historia.blogspot.com/&prev=/search%3Fq%3Dlugares%2Bcon%2Bhistoria%2Bblog%26client%3Dfirefox-a%26hs%3DauE%26rls%3Dorg.mozilla:es-ES:official%26biw%3D1920%26bih%3D978

FifthElephant, those look very good. �Who does the 7th or the 16th in Quake? 

I wouldn't want to do the 7th, but I reckon the 16th is doable. 

It was an ironic comment for everyone as i thought first that those would be the ones that would have the less probabilities to be mapped.

The seventh one is doable too, but boring to play, as it is mainly a single huge room. Just have to do a part of it (e.g. 10�), and then copy, paste and rotate it several times (36). Easier said than done.

The 16th, i said it because its underwater, and gameplay underwater isn't usually well received in Quake. 

Glaciers, crevasse, arctic: http://www.dianeburko.com/polarinvestigations/?p=181 (check out the rest of the blog) 

Pictorial Encyclopedia of Historic Architectural Plans, Details and Elements

Reprint of a book originally published in 1923, so there's nothing modern in it. Well made, durable construction. Bought my copy from Barnes and Nobel back in 1998 and it's held up very well.

About 140 pages. Pen and ink line drawings on the right hand page with brief descriptions on the facing page. Lot's of stuff to draw inspiration and potential ideas from.

Probably should be able to find a decent used copy for under $5 including shipping. 

that's cool, i actually have this related book at home:

http://www.amazon.com/Illustrated-Dictionary-Historic-Architecture-Dover/dp/048624444X/ref=pd_bxgy_b_img_y 

:D 

The Pictorial Encyclopedia of Historic Architectural Plans one is really solid