Marriott is offering 10 Bonvoy points on every USD spent on city sightseeing tours, Hop-on Hop-off tours, museum tickets, culinary experiences and hundreds of other tourist activities worldwide. You need to book these activities via Marriott's activity booking mini site in association with Place Pass. IHG has a similar offer for booking activities in partnership with Viator.
Online activity booking is very convenient while traveling. Saves time, helps confirm plans in advance and generally a lot better rate too. Plus I am game for anything that saves me from dealing with touts.