They should show up on the map of the building. When you're outside you can click on the major buildings that you can go inside of and it will show you the map of the insides and any riddler stuff in there.
Though some areas have informants inside and the stuff won't show up until you obviously interrogate them.
On the topic of the robin and nightwing DLC, how do they control in combat? Is it a mix of really fast catwoman and the tank-ish Batman? Are the battle animations cool? When they get a sale I'll probably buy them both but I'm just inquiring ahead of time.
I haven't played Nightwing enough to comment on him yet, but here are some thoughts on Robin:
*You get two new 3-d trophies on top of the one you unlock from the main storyline. You get an Animated Robin trophy (looks cel-shaded and just like the Teen Titans Robin) and you get a Red Robin trophy (hard to describe, but he has a red cape).
*All three of the above Robin trophies (story mode Robin, animated Robin, and Red Robin) are selectable in the challenge mode! I love playing as Animated Robin. His cel-shaded character model looks so pretty in this game.
*Robin has detective vision! So unlike Catwoman, you can very clearly see all the threats in the room: who has guns, who doesn't (if they've been disarmed), who has body armour. It doesn't keep track of the number of hostiles remaining like Batman's detective vision, but aside from that it's identical. This will be a huge help in the predator missions. I recently finished all of Catwoman's challenges (including the campaign ones) before downloading Robin and so I was so used to barely being able to make out enemies in Thief Vision and not being able to distinguish between armed/unarmed and armoured/unarmoured enemies, or not being able to pinpoint henchmen with jammer backpacks.
*Robin has a smoke pellet and a cape! And lots of cool other gadgets. His arsenal is much more versatile than Catwoman's. It's so nice being able to glide places instead of being forced to take a giant leap every time I jump like with Catwoman. And smoke pellets should make predators a ton more manageable. Robin's gadgets include the following (I have a feeling I'm missing at least one gadget in the list below):
1) Zipline: This does not work like either the batclaw or the line launcher. It allows you to do a "Zipline Kick." Aim towards an enemy and you'll quickly launch towards them kicking them down.
2) Shield: The shield can be pulled out to deflect bullets (can only deflect bullets from the front) and can be used to bash an opponent.
3) Explosive Gel
4) Shuriken/Remote Shuriken (they work exactly like the Batarang)
5) Snap Flash: This is kind of like explosive gel, except it can only be planted on an enemy, and cannot be planted on a wall or the ground like explosive gel. Once it's planted on an enemy, whether that enemy is dead or alive, it can be detonated. If the enemy is alive, he'll be knocked unconscious when you detonate. If he is already unconscious, it will knock out nearby henchmen who are investigating the unconscious body once you detonate.
6) Smoke pellet - no explanation needed here.
*Regarding combat - he's slow, really really slow, and no where near the speed of Catwoman. I think he's a little slower than Batman too. His attack animations are nifty though. Instead of his fists, he fights with a single baton that he wields two-handed. The baton sometimes magically extends whenever he's doing special moves. Also, the baton transforms into the aforementioned shield whenever you use the shield bash - that animation and the accompanying sounds are slick.
*I haven't tried Robin's new predator map yet, but his combat map is soooo freaking cool! It's a side-scrolling map - you fight on a moving freight train. You move seamlessly from round to round by walking into new train carts, instead of having the screen fade out and fade back in like every other combat map when loading new rounds.