If you want to specify additional logic for not-found routes, instead of just throwing default 404 page, you may create a special Route for that, at the very end of your Routes file.
1Route::group(['middleware' => ['auth'], 'prefix' => 'admin', 'as' => 'admin.'], function () {2 Route::get('/home', 'HomeController@index');3 Route::resource('tasks', 'Admin\TasksController');4});5 6// Some more routes....7Route::fallback(function() {8 return 'Hm, why did you land here somehow?';9});