From Lima: Pachacamac, Barranco & Chorrillos Private Tour

You can only submit a review or rating of an experience to Viator if you were the person who made the booking through Viator. Before publication, each review goes through an automated tracking system, which collects information for each of the following criteria: who, what, how, and when. If the system detects something that contradicts our publication criteria, the review is not published. When the system detects a problem with a review, it may be automatically rejected, sent to the reviewer for validation, or manually reviewed by our team of content specialists who work 24/7 to maintain the quality of the reviews on our site. In some cases, we will also send you an email asking you to validate your review before it is published. All you need to do is click on the link provided in the email. After publication, our team checks each review reported to it as not meeting our publication criteria. Tripadvisor reviews that appear on the Viator site are subject to the same checks and moderation processes as set out above. It is not necessary to have booked an experience through Viator (or Tripadvisor) to submit a review of an experience to the Tripadvisor site.