I booked several tours through Viator tours, and Viator then booked through Arctic Adventures. The next time I go to Iceland I will book directly with Arctic Adventures, as it takes out the middle-man, they have an office in downtown Reykjavik that's open until 10pm, they have a wonderfully helpful and informative staff in the office and on the phone, and it's much easier to make changes directly through them, rather than through a tour warehouse (like Viator). Arctic Adventures will tell you EXACTLY! what to expect on your tour (info not given by middle-men) so that you pick the right tour for your adventure level! I went on the Lava Tubes cave tour (make sure you're comfortable in small spaces!) and Glacial Hike/Waterfoall tours which were both wonderful. The safety gear fit well and the guides provided clear directions for how to stay safe during the trip through the lava tube and on the glacier. The guides were also great at telling stories along the car ride to our destinations. I'm looking forward to my next trip!