Safety - parents are able to allow their kids to frequent the neighborhood without concern, because only those players invited can be there.
Access to friends - neighborhoods are established by a group of friends, family or players with similar interests; only those invited can come.
Gathering place - this is where players can meet and tell stories of adventures, plan new adventures, plan competitions, share information, etc.
Display area - this is the area where players display scores, photos and trophies from their adventures to other Ages.
Modification/customization - players are allowed to customize their neighborhood within parameters - things like choosing a certain lighting scheme, determining building usage, display areas, color, etc.
Controlling "mayor" - mayors will make decisions regarding the neighborhood rules, customization, building usage, etc. (individual who starts the neighborhood will be the mayor).
Small scale repeatable gaming - there are areas where players can gather to play repeatable/competitive games.
Education - .hints/tips for those who want to share in the neighborhood - people who's opinions you trust.
Always has a view to the city - all neighborhoods will face the city (island) and be located along the cavern wall, hopefully slightly skewed so that every neighborhood doesn't appear to be in exactly the same spot.