Use the following code to create a list of categories in WordPress.

<?php
//$taxonomy = 'genre';
//$orderby = 'name';
$show_count = false;
$pad_counts = false;
$hierarchical = true;
$title = '';

$args = array(
//'taxonomy' => $taxonomy,
//'orderby' => $orderby,
'show_count' => $show_count,
'pad_counts' => $pad_counts,
'hierarchical' => $hierarchical,
'title_li' => $title
);

?>

<nav id="menu-blog">
<ul><?php wp_list_categories( $args ); ?></ul>
</nav>