This adjustment was made in Lab mode - I actually cheated and used CurveMeister from the RGB colour space (and you could use EasyCurves).
These are my curves...
The L channel curve has increased contrast by moving the left end in
(I set the Shadow point to the left of the main stairs)
and then bent a lot to improve the contrast in the distant at the expense of the
foreground - which has been darkened considerably.
The a and b curves saturate the colour Green and Yellow colours quite heavily, a little Magenta but no Blue change.
This adjustment, more or less, removed all the haze in the middle distance.
However I might have over coloured the wall - in which case a simple adjustment using the BlendIF slide thus...
will give this image
although I prefer the darker red, as it is moderately early in the morning in September and the sun doesn't look that high.