I paid for three Viator tours while on a Mediterranean cruise in May. Only one went flawlessly (a cooking class in Mykonnes), and the other two had problems. Our voucher for a 3.5 hr. tour of Vatican City in a small group of 10, purchased 4 months in advance, became the nightmare of our 18 day trip. Viator obviously is the booking agency the connects travelers worldwide with local agencies who conduct the tours. Most of the local agencies are good (used them previously in Europe and Canada), but THINGS ONLY WORK IF VIATAR GIVES YOU THE CORRECT INFORMATION. We arrived at the Vatican steps at 2:00 for a 2:30 entrance and could not find the company stated on our voucher on any of the guide's flags or signs. During our frantic search 3 nice Vatican officials tried to assist us and agreed that no one from that company name was there. Ironically, an Ecoart tour guide noticed the Viator symbol on our voucher and said "yes, we use Viator but we are not the company you're looking for." At 2:45 I was almost in tears so we purchased tickets with another group, and we paid 56E each on the spot to join another group of about 20 people. It was a great tour with the non-Viatar group, but later it was not easy getting Viatar to admit their fault and they never apologized. I was livid when the second Viatar rep said that Ecoart said we never showed. I told her that we had spoken to them twice but that Ecoart was NOT the name of the local agency printed on our ticket so neither of us thought we should be in that group. Only after writing a long description of our nightmare in the sweltering heat, did they seem to believe I was there and gave us a refund with words to the effect that they were doing us a big favor- no apology, nor denial, for printing the wrong local name on our voucher. The previous day, we enjoyed a terrific 8 hr. Almalfi coast tour with Worldtours of Naples that we purchased through Viatar. The tour exceeded our expectations except that the tour description had said we would be part of a small group of 16, and we counted 30 on the bus. The same thing happened to us on a Viatar trip in Canada that promised group of 12 and it was 20. I don't know if local groups increase the number, or Viatar just buys that many spots from them, but either way the customer is not getting the smaller group experience they pay for. I will do my best to avoid Viatar bookings on future trips and suggests that others do the same.