For as long as most art historians can remember, landscape painters have been packaging their wares in squares...well, actually, more often, in rectangles. That shape seemed best able tp accurately accommodate their broad visions of space and earthly delights. Sometimes the width became two or three times the height to reflect the nature of nature. This no doubt resulted in the Cinemasope, Cinerama, and IMax screen shapes we've seen in our lifetimes. In 1787, however, an Irish artist by the name of Robert Barker decided there must be a better way to depict nature. He called it Nature a coup d'oeil, and jettisoned the rectangle in favor of the circle. This representation he felt was most ideal for capturing the endless realm of structures found in cities, and with the ever-improving printing technology of the time, he made a fortune.
Basically, what they were were round postcards. The viewer could hold one, turning it as he mentally turned 360 degrees, picking out landmarks great and small, each numbered, with a corresponding list of names on the back. Rural areas were accompanied on the back by comments about life in the country. Taking a cue from this development, there later evolved larger panoramas on paper or oil cloth of all the great cities of Europe. By mid-century, these panoramas were replaced by dioramas, placing the viewer in the MIDDLE of the circle, which got ever larger and larger, eventually involving specially designed buildings, a trend which reached its zenith after the civil war when 360 degree representations of famous battles were painted. These were often accompanied by skylights and three-dimensional foregrounds which blended the real with illusionary paintings.
Around the same time, "optical cameras" were introduced that no only made painting dioramas easier, they eventually made it possible to take photos in 360 degrees by synchronizing the turning of the camera and the movement of film in such a way that the light coming through the lens was able to "paint" an image along a strip of film as the camera rotated. Rather than a circle, the shape of the landscape (or more likely, a cityscape) became that of a cylinder, and depending on the camera, they were often up to three feet in diameter. Such cameras were large and bulky, and required specially built structures to house them. A "Rotonde des Panoramas" was constructed first on the Champs-Elysees in 1841, another went up in Munich in 1880, and later in the Rotunda of Vienna's Prater in 1882, and Berlin in 1883. Shot in black and white, artists found work coloring the photos with thinned oil paints. No longer mere picture postcards, these photo-dioramas were sold to enterprising businessmen who installed them in small kiosks, charging admission for a "trip" to Paris, Berlin, or Munich. Recently, a former student who'd spent several months studying in Italy, showed me a book he'd purchased just before leaving Florence, with fold-out 360-degree color photos of the Piazza Del Vecchio, the Piazza Navona in Rome, and St. Peter's Square in Vatican City. The traditional rectangle (albeit a very wide one) had reasserted itself.