Basically, it is a social networking site that lets you visualize all activity within a city or given area in 3D. It also allows its users to learn about the hotspots and events that are scheduled for the future.
In their own Words:
YouCity is a neighborhood-based social network site that helps you connect with local people sharing the same interests. It is a website where you discover on a fun 3D map the city hotspots and exciting local events through people like you.
YouCity combines real-life neighborhood context with social context to provide the first true integration of online social networks with local geography. It creates online neighborhoods that not only mirror every corner of the real world we live in but also change the real world and benefit people's everyday life through revolutionizing the way people creating and sharing local information and interacting with each other and places around them.
it is only available for New York and San Fransisco...