Two buildings.
Futurism was a staple of the 20th century, and from the early Industrialists of the late 19th century and early 20th - to the Space Age dreamers - what effectively looked "modern" has changed. Lets take a look at two architects and their "futuristic" structures at the time.
Antonio Gaudi
The Catalan Maverick
Antonio Gaudi was a Catalan architect known for his keen interest in nature, and therefore natural forms. He was influenced primarily by Modernisme, an expression of early modern architecture. His unique style was also typified by his structural design - which fully realized the power of the Catenary arch.
A Catenary Arch, while it sounds complicated, is actually an elegant concept. As gravity pulls objects down towards a point - due to the nature of acceleration in a material - the inverse can be used if you were to flip the object over. This creates the most structurally powerful possible load bering arch for the amount of materials used to create it. Gaudi regularly used strings tied to bags of sand to calculate his structural models.
Model of the Catenary Arch
Buckminister Fuller
The futuristic dreamscapes of Fuller were an extension of the optimism and intellectual restlessness of the late 20th century. His designs frequently used triangles in the confines of a 'geodesic dome' - which when tessellated together, can hold incredible stresses for such a thin structure. Fuller's designs for these structures were to make urban life more efficient, through the use of solar warming and water collection.
Ironically, Fuller's belief in the most efficient from the least materials ultimately culminated in his magnum opus, the aforementioned geodesic dome.
Compare and Contrast
Whereas Fuller's structure was about being lightweight and conservative with materials - Gaudi's structures were about using materials normally found in heavy masonry in a way that made them feel lightweight - even in their native application. Fuller's vision was for an architecture that was more futuristic - something that could bring more efficiency with less materials. While Gaudi used stone to achieve his visions, his was remarkably similar with Fuller in the scope of his aesthetic ambitions. Although using stone, he wanted to use it in ways that made it seem organic and light.