The Steam Summer Sale is on! As most important title Civ6 is on sale, with a 90% discount, down to 5.99€, with also the Anthology and Platinum being discounted by 86% and 91%.
Obviously, besides the Civ games there is a lot more on sale, e.g. Old World is discounted, the Total War Franchise has various titles on sale, mostly 50% upwards, various Paradox games, as well as the Anno franchise.
Strategy and Wargaming .com also has an article with various interesting games here.