Need some suggestion about micro sites under same domain separate url

Hi,
I am looking for some solution where main site has its own main menu under same domain, when you click on any department under same domain it has its own main menu. its like microsite under same domain example

www.example.com (has its own main menu like "home, about us, contact us")
www.example.com/about-us (sharing same main menu)
www.example.com/department-1 (has its own main menu like "About, Programs, Faculty")

example main site
https://www.aus.edu/

example sub site
https://www.aus.edu/caad

both are sharing same url.