Oil
The first few steps felt just the same. I felt no heavier, the air I breathed in felt just as sufficient for my body to fuel off of, all the rules felt the same.
But the giveaway was in my eyes. They moved the same way in their sockets, scanning at what felt like the same speed they always had. But the images they captured were wrong. Objects dragged together like a large brush wiping over a still damp oil painting. Streaks of colour from one building smeared and settled in with the colours of the next. When I focused they started to steady out, settling back where they belonged, but then it looked fake.
I rubbed at my eyes instinctively. Maybe I had been crying, or drugged, or had some kind of strange contacts inserted in the short time I had been unconscious. But like the rest of my physical body, they felt exactly the same. I was not dizzy. My heart rate was not elevated. The only thing amiss was the visuals my eyes fed my brain. Was it me or this place? I could not tell which was at fault for the error.