This is probably the least popular place to land, which makes it the safest one. It is no surprise, since the Mire is just one big swamp with very few buildings. However, if you go to the northwest, you will find a prison building with some excellent loot inside.
Also, there is a large tree with a treehouse that may spawn up to 2-3 chests at a time. This will give you all the most important starting loot for the beginning of your survival journey in Fortnite Battle Royale.