Strongholds is an Unearthed Arcana article in Dragon 395. [Dr395] The base price of a stronghold is 25000gp, equivalent to a level 15 magic item. It comprises of 300 squares of floor space, and is considered save and secure for most cases. If it is in a remote location, it may cost 50,000 gp if on a mountaintop or deep wilderness, or 125,000 if in a fantastical location such as underwater or on another plane. Strongholds may be purchased, conquered or constructed. If constructed, it may need around 1d10+5 months or 1d10+5 years depending on the complexity of the stronghold.