Wikipedia
TourRadar
TourRadar is a travel website where travellers and tourists can book a group tour, as well as featuring user-generated reviews of individual tours and of the Tour Operators. It claims to have more than 20,000 tours available from more than 250 different tour operators worldwide, and acts as an online marketplace for third party tour operators to list their tours so that users can find them. As well as offering booking and reviews of tours, they also allow travellers to meet before their tour departs through their iOS and Android apps.