How to rewrite custom post type with custom taxonomy urls?

I am working in a WP multisite which runs on a classipress theme and there is a custom post type “ad_listing” and custom taxonomy type “ad_cat“. Now the url is like this

http://www.example.com/ad-category/transport/

I need to rewrite this URL so it looks like

http://www.example.com/new-york-city/transport/

and categories are nested so it can be nth level.

Please help me how to do that with wp rewrite rules.

Thanks in advance.Any help will be greatly appreciated.

When you are adding a custom taxonomy you are able to declare a rewrite slug –

$labels = array(
    'name' => _x('Name', 'taxonomy general name'),
    'singular_name' => _x('Singular Name', 'taxonomy singular name'),
    'search_items' =>  __('Search Items'),
    'all_items' => __('All Names'),
    'parent_item' => __('Parent Item'),
    'parent_item_colon' => __( 'Parent Ites:'),
    'edit_item' => __('Edit Item'), 
    'update_item' => __('Update Item'),
    'add_new_item' => __('Add New Item'),
    'new_item_name' => __('New Item Name'),
);

register_taxonomy(
    'ad_category',
    array('post-type1', 'post-type2'),
    array(
        'hierarchical' => true,
        'labels' => $labels,
        'show_ui' => true,
        'query_var' => true,
        'rewrite' => array('slug' =>'new-york-city')
    )
);