I have used Viator to book local tours in S.America and in Cambodia this year, and have been very pleased with the experiences. The website is easy to navigate, and has a huge range of tours on offer all pre-bookable online at reasonable prices. There is a mechanism for queries which seems to work efficiently and promptly. I have found the local firms I have booked via Viator to be reliable, friendly and to have a good standard of spoken English. The tours have all been good, often very good and sometimes excellent. In the absence of local knowledge, Viator has become my first point of enquiry for booking local tours in exotic parts of the world.