I have never seen them before. They appear a little random. They were there for a while and now after a few hours they have disappeared from my map.
Maybe that are places with good coffee? 
They look like bookmarks (linked in the top right menu) … but I couldn’t reproduce the situation where they’d stay on the map during page navigation (as an example, you can use Route Builder starting on an activity page, navigate through the site to a city page, and it’ll retain everything about your Route).
