How it works
On a free tour the guide is included and tips are left out, according to the tour listing. That means you decide at the end how much to leave if you liked the walk. Before booking, check the departure, the duration and the guide's language on the listing, because not all groups run in the same language.
How long it takes and where it starts
The tour listing says it starts in Cusco and lasts 2 to 2 hrs 30 min. Count on that full time and leave a margin before your next plan of the day. Keep in mind that Cusco is a city for walking, so it is worth wearing comfortable shoes and bringing some water.
What to expect and what is left out
It is a way to get your bearings in the city before deciding what to see at a slower pace. The listing shows only the guide as included, so any admission, meal or extra transport is on you. If you later want to enter the sites around the city, compare with the four ruins visit.
When it suits you
It works for your first day in Cusco, while you are still getting to know the center. If you prefer a tour of several hours with a transfer, look at the guided visit of the four ruins. If you are after a plan for after dinner, there is also a night free tour with its own listing.