<p>カテゴリー</p>
<ul>
    {% for category in categories %}
        <li><a href="{% url 'index' category.slug %}">{{ category.name }}</a></li>
    {% endfor %}
</ul>

<p>場所</p>
<ul>
    {% for location in locations %}
        <li><a href="{% url 'index' location.slug %}">{{ location.name }}</a></li>
    {% endfor %}
</ul>

<li><a href="{% url 'index' category.slug location.slug %}">{{ location.name }}</a></li>