Final answer:
Mies van der Rohe's ornamental and structural expression is characterized by minimalist design, innovative use of materials, and the integration of form and function, encapsulating the 'less is more' aesthetic. His work is part of the broader Expressionist architecture movement, which sought expression through form, and contrasted with the ornamentation-focused art nouveau style.
Step-by-step explanation:
Mies van der Rohe's approach to ornamental and structural expression is exemplified by his minimalist and innovative designs, his application of new technologies and materials, and the integration of form and function. His famous adage, "less is more," articulated his philosophy of simplicity in design, where every element of a building is required to contribute to multiple visual and functional aspects. For example, a floor might also serve as a radiator, or a fireplace containing a bathroom, to promote functional simplicity and spatial efficiency.
The incorporation of Expressionist architecture elements in Mies van der Rohe's designs also connected to the broader movement that emphasized the use of novel materials, formal innovation, and often dramatic massing. Projects like the design for his skyscraper in 1921 broke away from traditional masonry cladding with its innovative steel skeleton and glass cladding concept, reflecting an openness towards the modern industrial era and its new aesthetic potentials. In contrast, his Barcelona Pavilion reconstruction demonstrates how minimalism can harmonize spatial usage and architectural components, serving as a testament to the Bauhaus movement's integration of design and craftsmanship.
Moreover, Mies van der Rohe's work expresses a distinct contrast with the preceding style of art nouveau by freeing the form of the whole building, rather than primarily focusing on ornamentation. Expressionist architecture sought to embody inner experiences and artistic expression through unique forms, such as the dome shape and varied geometric structures that characterized the movement.