rampart
/ˈræmpɑːrt, ˈræmpɑːrt/Definitions
1. noun
a defensive structure built around a fort or other stronghold, typically made of earth, stone, or brick.
“The medieval castle had a high rampart that overlooked the surrounding countryside.”
2. noun
a barrier or obstacle that must be overcome.
“The steep rampart of rocks made it difficult for the hikers to climb the mountain.”