|It does have a very fantastical look that would make it ideal for adventuring.|
Seeing the castle immediately got the hamster running in my head and I started to speculate what this thing would be like in a fantasy setting. The first thing that jumps out at you is that Neuschwanstein is not a military fortification. There are no outer walls or any kind of protection save for the hill it's built on top of. So clearly not meant to withstand a siege or hold territory. It wouldn't need to do either if it was located within the interior of a kingdom or empire where having a military fortress wouldn't be needed.
|Ludwig II, King of Bavaria.|
Of course, it wouldn't have to belong to a monarch. It could just as easily belong to a powerful member of the nobility such as a duke or an earl. There too is a potential source of intrigue for a campaign. A castle such as Neuschwanstein Castle would be pricey to build. Indeed, Ludwig II accumulated huge debts because he insisted on funding the construction with his own money and loans. That level of expenditure could draw the attention of the monarch's court and make them very curious about where the good duke or earl (or duchess or countess) is getting the funds for such endeavors.
|A castle full of mystery and intrigue.|
- A member of the royal court, likely through a less visible functionary, hires a group of adventurers to pay a visit to the noble and try to discover the source of their funding. The infiltration is left to the party, but discretion is preferred by their employer.
- The noble in question is found to have been skimming tax revenue or involved in some less than legal operations. The court wants them in custody but is unwilling to go about it in public for fear of triggering a rebellion or civil war. The party is employed to find a way to extradite the felonious noble back to the capital where they can be formally charged. Alternatively, the court decides to send the party to take care of the problem. Permanently.
- Another alternative is that the royal court decides to make an example of the noble by sending a force to seize their castle and take them into custody for a very showy trial. The adventurers are sent to reconnoiter the area for secret entrances/exits that would allow the approaching soldiers to take the castle from the inside. Failing that, they're to try and sabotage and compromise the castle's meager (because again, this thing isn't a fortification) defenses to make the royal fore's job even easier.