Leave Vernon's apartment for the first time and find the skater boy, then use the lipstick on the skater boy and Nico will say something similar to "There was no way I was going to do that!" Walk down the street and pass the park. Usually when you do this Nico will say "I considered leaving the area" and you will be prompted for a destination. Instead, a loading screen will appear and you will enter a hidden area. It has a dog that walks around and a bridge that crosses the river. When you walk down the bridge far enough Nico will say "I considered leaving the area," and you will be prompted for a destination.