Viator charge 20%-25% and now they are now owned by TripAdvisor.
Last year, TripAdvisor started putting a lot of pressure on my Naked Tour Guide company to list with Viator. We refused to hand over such a huge slice of our turnover, and accordingly our visibly on TripAdvisor was instantly diminished. Overnight, we went from a situation where 80% of our guests found us on TA to less than 20%.
Also, TA started cloaking their referrals, so we couldn't trace traffic coming to our website from them anymore. It created the worrying impression that suddenly we were invisible on TA, unless we signed up to Viator. Accordingly, they kept pushing Viator, hoping that we would buckle to the pressure and surrender 20%. I think the best analogy this business practice is the Speedy Boarding Sketch.
Then late last year, I was contacted by two small tour operators in Amsterdam and Paris who had experienced the exact same phenomenon. As we had all suffered the same tactics, we decided to band together and we have formed Tourlings - an independent collective of small group tours. We actively recommend each others' tours in Prague, Amsterdam, Bratislava, Paris and Istanbul and unlike the major resellers we do not extort any fees from our members. It is an arrangement based on mutual respect and cooperation, and is designed to help people find easily find the best small group tours in our member cities.
As for the brewery in Beroun, it is really excellent. They also stock an excellent cyclists beer (very weak, about 1.4%), which is the closest thing available to the old-style beer that was consumed in mediaeval cities.