Cummins Engine Factory, by Roche & Dinkeloo, 1965 Darlington, UK; photo by Photographs Team 3
The Twentieth Century Society has created a list of the most endangered English buldings, The Risky Buildings List:

Today, many important buildings of the twentieth century are not only neglected and unappreciated, but are severely decaying and under serious threat of being demolished. The majority of these buildings are made from concrete. Crumbling and stained, they lack the romance of polished marble or rough-hewn stone. Desolate car parks and redundant shopping centres seldom attract the sympathy and support of the public, despite being of potentially great architectural importance.

One building which instanly caught my eye was the Kevin Roche and John Dinkeloo Cummins Engine Factory located in Darlington, UK:

This is the first independent work of Kevin Roche and John Dinkeloo, former associates of Eero Saarinen. They continued Saarinen’s experiments with structural Neoprene gaskets – a means of fixing glazing derived from the car industry – and the Cummins building is the first in the world to use this system for internal partitions, as well as for external purposes, giving an exceptional totality of design. The delicate glazing pattern is contrasted with the use of a more heavyweight Saarinen material for the structural frame; Cor-ten steel. Cor-Ten steel is rich in manganese and vanadium. Within three years, it oxidises to a tactile rust-brown finish, which is maintenance free. Moreover it is claimed that it will last for 800 years.

The Darlington Cummins Engine Factory (1965) is an interesting counterpoint to the Roache & Dinkeloo Columbus Indiana Post Office and especially the Cummins Engine Company, Inc. Corporate Office Building (1983) both in Columbus, Indiana:
Cummins Engine Company Corporate Office Building by wistine
Roche & Dinkeloo have since fallen off the list of “exalted Modernists” but their exploration of materials and space make them worth a study in tectonics.
Read the complete list.