Aside from Detroit there are two other cities that have experienced sweeping economic and industrial declines. Turin, Italy is the home of Fiat, which struggled for years, and Youngstown, Ohio which felt the impact of reduced steel production.
Turin, Italy is the larger of the two and built its economy through industrial manufacturing during WWII. Like many cities, the end of the war meant the end of production. While FIAT still remained the demand dropped and so did the population. Two things helped them reverse those trends and one was the branding and product of FIAT itself. Its amazing what brands can do for cities like CocaCola in Atlanta for example or Nike in Portland, OR. The second thing in Turin was the 2006 Winter Olympics. It not only helped restore and industrial history, but it brought world attention.
Youngstown's glory days were throughout most of the 20th century due to the access and production of steel. When steel declined starting in the 1970's the city needed something to do with all of the factories and warehouses. Many were refurbished into housing or commercial buildings. This provided opportunities for work and creating a new vision. The other aspect of Youngstown was their willingness to shrink when needed. Whether that meant demolishing industrial building or vacant neighborhoods and closing streets they were willing to adapt and not helplessly cling to the past.
I think their is a lot to be learned from these two cities especially when revisiting cities of different sizes and different cultures. Hope you do too!