Sentence:  From the ground, Colombo's port does not look like much. Those entering it are greeted by wire fences, <WSD>walls</WSD> dating back to colonial times and security posts. For mariners leaving the port after lonely nights on the high seas, the delights of the B52 Night Club and Stallion Pub lie a stumble away. 
Meaning of the word marked with <WSD> tags:  A structure built for defense surrounding a city, castle etc.