Fast detailed offline maps for travelers, tourists, drivers, hikers and cyclists created by MapsWithMe (Maps.Me) app founders.
Organic Maps is one of the few applications nowadays that supports 100% of features without an active Internet connection. Install Organic Maps, download maps, throw away your SIM card, and go for a long trip on a single battery charge without any byte sent to the network.
I've always had issues with this app. I think the issue was not every store or address was listed and if it did have it, then it would take forever to load the route to get there.
Sometimes it tells you to drive through a fence, over someone's yard, and into a lake. If you're from the TomTom/Garmin era it'll be nostalgic. Still, I've been using it for a long time and it's been my favorite for a while. Early days were a little rough, and sometimes the routes are still a little weird.
I discovered some time ago that it is another Estonian piece of tech (well, at least the org behind it is). Maybe that is why it works so well in Tallinn, but indeed it's great!