Follow the girl.

As you approach the building you saw the young girl enter, Harley places her arm across your chest halting your progress.

"Strange" she muses "I've blown up pretty much every apartment block in Gotham in my time, but I don't recall ever seeing this place before"

At first glance you can't see any difference between this one and the rest of the structures that scar the landscape, but then you realize what she's getting at.

"Is it me or does it seem...brighter than the rest?" you ask.

"Yeah" Harley replies "It's like it's bathed in perpetual sunlight. I've got it!" she yelps startling you "This must be one of them things that Vicki was going on about. You know a what-cha-ma-call-ems"

"An anomaly?" you offer.

"That's it!" Harley squeals jumping on you, wrapping her arms around your neck and planting a massive kiss on your lips.

"Seems the intelligence boost is paying off"

As she drops down and turns around you slap her ass "So, shall we see what lurks inside, m'lady?"

"Good idea " she winks and heads towards the door.