Serving multiple pages from the same URL

We want to implement something like facebook, where the login page and the web application are served at the same URL i.e., www.facebook.com

Currently in our app we have the login page being served at

www.ourapp.com

and the web application running at

http://www.ourapp.com\portal

We are using Nginx and it looks like Nginx does not allow 2 root/index directives to be served from the same location (example: www.ourapp.com), therefore we have to have to have 2 different customer facing URL's. Is it possible to conslidate the 2 URLs under www.ourapp.com?