Old Port el Kahlia is part of Monastir's historic seafront, where the harbour, ribat, and old defensive fabric sit close together. It is not as monumental as the fortress, but it helps explain why this coastal town grew where it did.
Use it as part of a slow walk rather than a single destination. The interest is in the mix of boats, stonework, sea views, and the way Monastir's religious, military, and maritime history all press against the same stretch of coast.