Detailed rules for building strongholds give your characters something to spend all that money on! You can build castles, guilds, secret island retreats, or underground lairs.
Your stronghold grants you special benefits which you can use while adventuring! Perhaps a temple in your castle gives you the favour of your god, or a blacksmith ensures that your weapons are of the highest quality. Choose the rooms and facilities at your stronghold, design its defenses, hire guards, and give it special properties.