Will grouped Laravel routes be cached? Where are they cached?

As stated in the docs

Closure based routes cannot be cached. To use route caching, you must convert any Closure routes to controller classes.

But if I want to group routes I can make the route itself point to a controller (function) but the group will still be a Closure

Route::group(array('prefix' => 'admin', 'before' => 'auth'), function() // Closure
{
    Route::get('/', 'Examplecontroller@bla'); // non Closure
});

Maybe for research purposes: Where are the routes cached?