I booked a tour of the Vatican Museums through Viator. I followed the instructions for picking up the tickets, but the tour operator never showed up and did not reply to my messages. I contacted Viator for a refund, but they refused, citing that their "investigation" showed the tour operator had done their due diligence, even though I provided screenshots of the messages I sent and the lack of any messages received. Viator partners with bad-faith actors and they know this, but they will not take responsibility for it whatsoever. DO NOT USE VIATOR, unless you want to completely waste your time and lose money for nothing.