In the wake of World War I, the United Kingdom developed a powerful yet relatively low-tech architectural system for detecting incoming enemy airplanes, the remnants of which can still be found across the countryside.

Starting in the 1920s, these concrete sound mirrors were built to passively gather, reflect and concentrate acoustic waves, directing the sound to listening posts on the ground — key infrastructure in an extensive early warning alert system.

Incoming sounds were amplified by microphones and listened to by operators wearing headphones. Today, the remains of these mirrors are largely abandoned and in various states of disrepair, though some are protected with walls or fences and accompanied by historical plaques.

Based in Basel, photographer Piercarlo Quecchia discovered the existence of sound mirrors thanks to an album cover featuring one such structure. From there, he began the search out, find and photograph them — 13 in total (all that remain), most of which are located along the southern edge of England.

They may look monolithic and simple, but the curves of these structures were carefully calibrated. The designs were specifically calculated (and sound mirrors accordingly engineered) to pick up aircraft engine noises in particular.

“They represent an incredible demonstration of how sound can generate a physical form,” explains the photographer, in which “both the curvature radius and the dimensions of the dishes are studied and designed according to the sound frequency that they must reflect,”  He hopes the series will continue to raise awareness of these artifacts and bolster preservation efforts.

Like the airmail arrows that once guided planes from coast to coast across the United States, it can be easy to overlook such geometrically simple leftovers, at least until an understanding of their historical origins leads people to spot and appreciate them.

Traveling 23,000 miles over 4 years, photographer Marc Wilson has amassed an amazing collection of images spanning bunkers, gun emplacements, observation posts, command centres and other wartime infrastructure around Europe.

In his book, The Last Stand, 88 of the resulting images are arrayed to tell a complex story of different times and places. More than merely photographing these haunting remnants of war, however, Wilson also provides highly articulate reflections on everything from their site-specific purposes and aesthetics to their broader places in military and architectural histories.

“Composed of copious quantities of poured concrete,” many of these structures “defy and eschew any established aesthetic sensibilities: no hint of the classical, the gothic or the baroque here. Their geometries, purely contingent, were designed to resist the effects of the latest developments in projectile technology, their profiles shaped to deflect such missiles and avoid any direct percussive explosions on their structures.”

His shots are carefully composed and timed, often taking place in the early hours of the morning when eerie mists and dim lights grant the subjects a surrealistic atmosphere. There is a dreaminess and dreariness to his work that manages to make the objects captured seem both ordinary and otherworldly. Prints of many of the pieces featured in the book can be purchased as well.

Unlike even the most pragmatic warehouse of the time, “there was nothing speculative or arbitrary about the bulwarks of their sometimes bizarre and often ungainly forms: they were purely functional. While far from being graceful or classically proportioned, there is something visually appealing about the alien (and sometimes sinister) forms of those bunkers. Novelty does not quite describe this appeal: more surprise perhaps – a surprise that courts the sublime.”

Well known for stenciling big block-lettered phrases on walls around his native Newscastle, Mobstr made this piece is unusually blunt (as well as hilarious) – it amounts to a multi-part conversation between the artist and the city.

Even better than the original ‘COME ON AND PAINT ME WHITE AGAIN’ dare is the later response after the municipality indeed whitewashed the first work: ‘BOOORING’, using his same signature typography in black paint.

While not all of his work is quite so meta-minded as this series, this sequence remains a great illustration of how graffiti is generally temporary as well as contextual, and can have elements of humor and self-reflection beyond simple tagging. Some of his works are best seen in video form rather than via photographs, hence a few fun short films below.

A self-described minimalist, Mobstr explains the origins of his nom de plume, which are none too surprising: “It is a play on the term mobster which is someone who deals in organised crime. Most of my work is illegal however a lot of organisation goes into it. So as a joke I use the idea of it being organised (art) crime.” Also, he had a lobster named mobster.

Built in the 1860s and now on sale for half a million pounds (under $1,000,000) , it is hard to beat what this sea fort offers by way of views, a prestigious address (No 1 Thames) and amazing location (a short commute by speedboat from London).

The massive fortified structure (featuring 15-foot-thick walls) can be accessed by boat or walked to when the tide is low, albeit a long and muddy way to go. A BBC interview (screenshots above and below) shows both the problems and potential of this amazing piece of real estate – there are precedents, too, for converting old British army and sea forts as well as harbor bases.

The current owner purchased the property from the Crown Estate, which is to say he approach the “Lord High Admiral for Her Most Excellency Majesty Queen Elizabeth”, made an offer and had it accepted.

However, the buyer-turned-seller, himself a London resident, never found the time or funds to refurbish the place, so it remains in a state of partial decay – a would-be purchaser should expect a significant outlay for renovating the building’s exterior and interior alike.

Still, for someone with a fortune as well as a vision, it is hard to imagine a neater place to escape from city life. The firm WT Architecture has already taken a stab at conceptual designs for rehabilitating to structure (renderings shown above and below). As their drawings illustrate, there is a rich variety in terms of materials, shapes and spaces to work with, including a cavernous central stone circle with a tall wood-and-concrete watchtower and an adjacent rectangular brick structure (that could be used for guests).

As BldgBlog notes, “At first glance, it’s an amazing offshore castle, a fairy tale artificial island of 19th-century military Romanticism roughly an hour’s boat ride east of London. But don’t jump in too quickly, lest you overlook the ruinous state of the place: it needs almost literally everything, from plumbing to electricity, glass windows to the most thorough cleaning you could imagine, having been open to the oceanic elements for decades”

With some of her works it is hard to tell where the two-dimensional art ends and 3D objects begin, blending as they do into one semi-continuous, surface-defying series of overlapping murals.

“Charlotte Mann is a British artist known for her wall drawings and drawn room installations. These densely detailed 1:1 scale drawings of rooms in rooms are invariably made with thick black marker pen on a white ground.”

There is a gritty realism to the scenes she creates, reflected in the rough and unsubtle choice of drawing materials – one can expect shirts tossed over chairs, plants overflowing their pots and the occasional cat flopped on its back upon the window sill.

“Charlotte studied Fashion desisn at Central St Martins … and has been an associate lecturer at the University of the Arts London since 2001 she currently teaches at Central St Martins, Chelsea and Camberwell .”