Caution. Husband and I took a Viator day tour from Seville to Jerez and Cadiz. Only 4 people (including us) were on the tour. We had no "professional guide" as promised, so there was virtually no explanation of what we were seeing and no historical information. Also did not get to go to Puerto de Santa Maria or take a boat ride across the bay. Disappointing! Although we enjoyed what we did get to see and do. I recommend checking with Viator day before the tour date to see just what they're really going to give you for a tour. Mini bus was comfortable, other guests were congenial.
Many complaints have been posted in these forums about Viator. The only suggestion I have is to file a disputed charge with your credit card company, assuming you paid with a credit card, that you did not get what you paid for.
Thanks for sharing your experience.
Once again, Viator, seller of tours from other companies, has messed up another vacation. Over the years we have seen so many people come back and complain about their experiences with Viator. They are a huge rip-off and why they aren't reported to some international better business organization is beyond me.
Best is to not use Viator at all, as all of the tours that they list are tours offered by the other companies. Using the RS guidebooks, this forum, Trip Advisor and their reviews and forum, will help you find the original company and give advice on reputable tour companies.