Silence. Still silence. It shouldn't have been there.
Twilight took a deep breath in, felt the smell of the air around her, had another look around. Long since unthreatened by the prospect of enemy fire at that point, she'd flown up before to observe that portion of the city from above. Even Nightmare Moon's outburst had left it almost fully intact. The burnt signs in the ground her magic had left, covered by the rubble but still there. She'd moved all the debris aside to properly study the pattern, though there was not much she could learn by just looking at things from up there.
She had measuring equipment with her, but she hadn't used it yet. There was something about simply standing in the middle of the area that was enough to perceive how odd it was, something no amount of data would properly get across. The way the air smelled, the way it tasted if she opened her mouth to it. The subtlest buzz of something in the ground beneath her hooves. The silence. The place shouldn't have been as silent as it was. Wind didn't pass there. Even when there was wind outside, it didn't exist there.
There was no clear, defined limit to the area. When walking in, the changes felt subtle, hard to notice even if one was paying attention and looking out for them. Until, suddenly, they were not. Suddenly one noticed the silence, the way the air felt. Suddenly a look around at the singed white markings on the ground was cast and it felt like being somewhere else, somewhere alien. Twilight had gotten a couple other ponies there, without warning them. She'd watched their reactions.
She'd bring Celestia there eventually as well. At that moment she was leaving her be. After the torture she'd undergone and what had happened to Luna, she had a right to some time with herself, to sort out her ideas and find some rest. As much as Twilight did not like having to admit it, Celestia's sheer volume of knowledge still outclassed hers, so it was possible she would know more about the phenomenon she was observing or recognise something similar in it. She'd have her called, maybe later that day, maybe the day after. No. She'd go herself. She wouldn't put up any coldness for once. Celestia still deserved consequences for what she'd done, but at that moment her burden far outweighed her due punishment. She deserved help.
Twilight shook her head, focusing on the scene around her again. Ought to have been the silence getting her distracted. It was easy to think there, easy to let her mind wander elsewhere. She pondered the possibility of casting other spells there. Eventually she would have to try. There was a peculiar, not unpleasant itching on her horn. Something similar in her wings, in the spaces between each feather, it she spread them. She pulled out her measuring equipment, her notebook, and began writing down the readings she got. Maybe not immediately, not with everything else she'd been warned to keep track of, but she'd eventually figure out what was going on there.