While in the middle of the DLC, I noticed the there is a passage that leads to a huge cave, and there are draw bridges everywhere. I didn't know what it was for and thought it was for something later on in the game. But I just remembered about those caves and realizing, they had no purpose in the questline (specifically Dawnguard). Is the cave of any use? Is it part of the Vampire questline?

It needs to be explored in every corner.

Warning: I do not think you should read this before you have found the secret.

Ah, Florentius. I've barely spoke to him. So many things I have yet to uncover in Dawnguard!

Erm, actually...

You can apparently do both. I can confirm that the method I presented work.

Yep both methods can work nice rewards at the in end if you like blowing things up hint hint

Even a light spell works, the targets just have to be activated.
In any case, two nice unique books can be found there.

What unique books? Lusty argonioan bard can be found elsewhere. What other books might you be referring to?

That sounds eerily similar to

Ah, forgot that one. Not sure I picked it up. It made for an interesting, and disturbing story.

No, they're not, and we've been through this already in a http://www.gamesas.com/topic/1401014-the-mysterious-sun-fire-seals/. This cave is entirely unrelated to what Florentius was talking about. He was speaking of "caches." He says so. There are no "caches" here. There are "archery targets." These aren't the same thing. The caches he's referring to are the ones found on the main map labeled "Dawnguard Caches." They just won't open with the Sun Fire spell, which only means that Beth, for whatever reason, decided to make keys for them instead and forgot to update Florentius's dialogue.

EDIT: Granted,the above is speculation on my part, but it makes a heck of a lot more sense than "archery target = same thing as cache" or "cave with some treasure in it = same thing as a cache."

It is just an Agility Course. you go thru it with your Crossbow and have a little fun. Someone should make a thread about this and do a time-trial thing where people have to go thru the thing within a specific amount of time or post their best time.. Ye' know?

Players would just fabricate times anyway. I do like the time-trial thing as a concept, though. Pity there's nothing like that in the game. Like a training exercise that comes with joining a faction in the civil war. Some sort of gauntlet you have to run in a certain amount of time with your superior officer timing it.

I mean a thread about the whole time-trial thing. People will time themselves as they do it then post their best time(s) on the thread and the Original Post will have the top ten best times. Basicly, a little community type of thing that will be fun.. I have my own timer so I can time myself easily and would happily do it, if someone makes the thread. I kinda don't feel like making a thread right now.

I understood what you meant, but as I said, some players would invariably fabricate times making the whole thing rather pointless.

Still worth doing, if you ask me.

Start a thread then.