Technique

As other answers have already pointed out, the photograph employs an unusual perspective. This is accentuated by its subject matter: the Funkturm is a particularly slender structure with a relatively narrow base, which contributes to the almost vertigo-inducing perspectival effect. Contributing to this "off" feeling is also the fact that very few if any lines in the subject matter are parallel with the edges of the frame.

The photograph was taken in 1928. As other answers have already pointed out, Moholy-Nagy may have used a camera-on-a-stick approach or simply rotated the print. The former approach would have been greatly facilitated by the use of a small camera, and given that the Leica I had been introduced in 1925, one might assume Moholy-Nagy employed a 35mm camera for this acrobatic task. However, according to MOMA, the camera used was an Ernemann 6x9 (perhaps one of these or these) – so, medium format, and in all likelihood not a wide-angle lens. The film used was, obviously, black and white.

There are various (silver gelatin) prints of this photograph in different museums around the world. Some of the digital reproductions suggest chemical toning such as sepia, but some don't.

Meaning

To set the photograph in a reasonable context of interpretation, it is useful to consider the following quote, attributed to Moholy-Nagy in the George Eastman House Collection History of Photography (Taschen Bibliotheca Universalis, p. 517):

The reality of our century is technology: the invention, construction, and maintenance of machines. To be a user of machines is to be of the spirit of this century. Machines have replaced the transcendental spiritualism of past eras.

The Funkturm is, in a very real sense, a machine, and a construction which requires maintenance. Moholy-Nagy's quote may then be read as an exhortation to turn away from traditional aesthetics when "reading" the photograph: the aesthetics of past eras are useless, since they are of the wrong spirit. What we have here is a confluence of shapes, and arguably little of the photo makes sense, outside a purely abstract, formal frame of reference, unless one already knows what the Funkturm looks like from more conventional angles. What are the little shapes on the ground? (They turn out to be café tables, chairs and parasols – but they might as well be some unidentifiable radio tower apparatus, or little aeroplanes and petrol tanks, or a million other things, from this perspective.) Why do some of the shadows appear broken, and some appear to appear from nowhere? (Because what on first sight looks like the ground, at the "base" of the tower, is actually the roof of the restaurant at 52 metres – but this is impossible to read from the photo alone.)

Thanks to this perspective play, it is impossible to take the photograph as a literal, realist recording of the architectural structure. Ironically, the chosen high perspective flattens the structure into a mess of shapes, both linear and circular. This invites reading the photograph, as one earlier answer has suggested, the way a Bauhaus painting might be read. But a comparison is also invited with the photogram, a purposely abstract technique Moholy-Nagy also used to great effect.