Root is usually on Macintosh HD. The System folder is located at the root level. The proper name for the System folder is /System. The forward slash (/) is the root level.
or since '/' is sym-linked in your Volumes folder:
$ ls -l /System/
You can also do just 'ls', the '-l' option gives you long format. MacOS is a flavor of Unix (Darwin i.r.c.) underneath the hood. If you are new to Unix/Linux command line interface checkout :