Anyone any ideas about what this slope cutting through might have been about?

My dad is on vacation in Sicily, visiting the Castello Maniace. Despatched me this pic questioning what's occurring with the slope chopping by. I really like a puzzle however am stumped. Hoped some educated particular person may be capable to shed some mild presumably please!! TIA 🙂

https://preview.redd.it/3fetvr7r8vmb1.png?width=1080&format=png&auto=webp&s=863966ce991162be9dc8c7b555c72b9ef6e2c836