Configuring routes for controllers/admin subfolder

[eluser]CARP[/eluser]
Hi guys
I've created a CI app, and now I'll begin building an admin backend for it
I've set a default controller to be called (for frontend)

$route['default_controller'] = "frontend";

and now I've created an "admin" folder inside /controllers for putting the controllers related to admin area

How should I do the routes configuration?, so when users go

myapp.com/admin

they are shown or redirected to the default admin controller? Is this possible?

Thanks a lot in advance...