How do I get the url of single pages?
Craft creates an EntryModel for each Single Section, that allows you to access the URL property you are after. You can get the (one) EntryModel using the Section's ID and the first() method:

{% set singleSectionEntry = craft.entries.sectionId(singleSection.id).first() %}

&lt;a href="{{ singleSectionEntry.url }}"&gt;
    &lt;div class="link"&gt;{{ singleSectionEntry.title }}&lt;/div&gt;
&lt;/a&gt;