The Witcher 3: Wild Hunt tutorial takes place in Kaer Morhen, the stronghold of the witchers.
The Witcher 3: Wild Hunt is not a single open world game. It is divided into few major areas - White Orchard, Velen and Novigrad, The Skellige Isles, Kaer Morhen and few more smaller ones like Royal Palace in Vizima or Isle of Mists.
This division causes that you can not directly sail, for instance, from The Skellige Isles to Novigrad. Instead, you have to find signpost and use fast-travel option - additionally, it will be possible only, if you have at least one unlocked signpost in destination zone. Additional zones will be unlocked as you progress through the main story of the game.
The first open world location in the game is White Orchard. After few hours of exploring, doing quest and killing monsters here, you will be able to move on and visit Royal Palace in Vizima and then Velen, No Man's Land, Novigrad, etc.
You can continue traveling the world in search of witcher contracts and adventure after you finish main story - but everything will be as it was before the game's last chapter, and quests tied to the main story line will no longer be available.
Due to size of game world, I had to split ingame zone maps into a few smaller maps of sub-zones.
Be aware that my atlas contains a lot of spoilers and it is still work in progress and incomplete becouse I create it in my free time and game is huge.