Multiple level eager loading in Laravel?

Let's say I have these relationships

class Invitation
{
    public function invitedPeople()
    {
        return $this->belongsTo('App\Person', 'personID');
    }
}

class Person 
{
    public function apartments()
    {
        return $this->belongsToMany('App\Apartment', 'apartment_person', 'personID', 'apartmentID');        
    }
}

class Apartment 
{
    public function city()
    {
        return $this->belongsTo('App\City', 'cityID');
    }
}

My question here is, how many nested levels can we have when using Laravel eager loading? I've tried this query and it's not working, can someone suggest a work around for this?

return Invitation::with(['invitedPeople', 'invitedPeople.apartments', 'invitedPeople.apartments.city'])

via Chebli Mohamed