google '300 east randolph pedway' , its a glass walkway that connects 300 east randolph to the lakeshore east parking losts east of millenium park, its open to the public during business hours at 300 east randolph via lower level.
whitney young high school also has a walkway between two of their buildings . its a public school so im not sure what their process is like.
UIC also has a walkway between their student center east building and the student center east tower. it can be seen here
https://www.google.com/maps/@41.8726...7i16384!8i8192
also rush hospital on ashland and harrison has one.