You are awarded a Bastion when you reach 5th level. During downtime, you can invest gold into your Bastion to upgrade it with new facilities and services. At the end of a downtime, you can choose a number of available services equal to your proficiency bonus and gain their effects until the end of your next adventure. You can gain multiple uses of the same service unless otherwise stated. See the original post here.
Soldier Bastion: Barracks
The barracks is a Bastion of martial training, as well as a place of blade and armor honing and strategic discussion. As a soldier, you can use your Barracks to help augment your fighting abilities in coming battles.