While traveling through Europe it's nice to have a nicer-looking pair of shoes for those more formal occasions (or just to switch things up). The problem is that bringing a second pair of shoes usually takes up a significant amount of pack space. The solution? Lems Boulder Boots. These featherlight, zero-drop, mid-height boots are comfortable enough to walk all day in, stylish enough for around-town use, and then fold down to next to nothing. Another positive is that Lems has an "Eco-Rule of 50%"; which means they strive for less than 50% consumption in their manufacturing and distribution practices, compared to other footwear manufacturers.
Caveat: you might not want to wear these boot going through security, as unlacing them can be a bit of a chore. Also these are technically considered a "barefoot-style" shoe, so it may take some time getting used to.
Tip: Bring a few strong rubber bands (or better yet, some gear ties) to keep the boots folded tight while they're in your bag.