This is my new favorite map for open-area zombie survival scenarios that I construct with various npc and weapon mods, planting bases and supply caches throughout the city (mostly in the interiors).
I was pretty disappointed to discover the parking garage as well as the lower street area right next to it doesn't have any ai_nodes (or at least has no ai nodes for the ramps leading down to the lower road section). Stepping into these areas halts all npc movement entirely because the npcs do not know how to reach me.
In the next update, please please please go all out with ai_nodes! Anywhere the player can walk to without jumping or teleporting should also be a place an npc knows how to eventually reach even if they are on the other side of the city.
Thank you a bunch, this is a very pretty map, and I especially adore the 2d skybox texture you selected. Please don't abandon it like gm_bigcity had done to it. There's real room for improvement to make this the new most popular city map for gmod! The incredible scope and surplus of cool interiors makes it shine brighter already. Excellent work!

Edit: Also, I've down custom soundscapes before. If you need help with that I can help you.

Edit2: Also also, it seems the npcs freeze up in places you wouldn't think either, likely implying node graphs that they cannot access. Places like some of the parking lots, as well as near the border of the city at the wooden road blocks.