MB4 198a: Height of a Public Domain on Shabbos (345:10-13)
An item in public domain that is exactly 9 tefachim high and people use it then it's still considered reshut harabim even if it's less than 4x4 tefachim. What if it's less than 9 tefachim, between 9 and 10, or higher than 10 tefachim and not 4x4 tefachim?
The status of a ditch in the middle of reshut harabim.
The airspace of reshut harabim only extends up to 10 tefachim, above that it's a makom petur.