Can you show how you are trying to retrieve user city?

You can try namespacing City on the user model too - just so Laravel knows where to find it.

Yes, of course. This is my reflection code:

$rc = new \ReflectionClass($model);

if ($rc->hasMethod($fieldName)) {
    // This two calls below are returning: "Relationship method must return 
    // an object of type Illuminate\Database\Eloquent\Relations\Relation"
    $relation = $rc->getMethod('getAttribute')->invoke($model, $fieldName);

    $rc->getMethod($fieldName)->invoke($model);

    // And this one is returning: "Property city does not exist"
    $rp = $rc->getProperty($fieldName);
}

The namespace is not the problem, because without reflection I can access the relationship without any problem. Thanks for your answer!