Brooklyn Bridge Park

Is the halo around the buildings an in-camera artefact or has this been processed in another program? It's very obvious at first glance and detracts from the image.

I agree with you Antony, the halo caused by tuning the exposure.

most likely occurred through post processing

Its sometimes caused by darkening the sky too much or the wrong way.

Superb photo, gotta be careful of your overlay extending outside the adjustment zones tho....to avios the 'halo' effect.

You made a really nice image but that halo effect isn't doing it for me either. I'm going to guess that you made a selection with a feather to darken the sky. If so, perhaps using Hue/Saturation for the blues would have been another option.