Self-guided or guided walks focused on colonial architecture and history?

Galle Fort is perfect for this — you can spend hours walking the streets and examining the architecture with a good guidebook or local guide. Colombo has several areas with interesting colonial buildings that can be explored on foot. Some heritage hotels and cultural organizations offer walking tours focused on architectural history. Self-guided is possible with a good map and background reading, but a knowledgeable local guide adds a lot of context and access to buildings you might not enter otherwise. Jaffna also has a distinct colonial architectural heritage worth exploring.