Drifting Greyscale

For the city in the clouds weekly challenge on PixelJoint.

Greyscale color version of this piece.

Challenge:
Pixel Art Challenge: A City in the Clouds

Show us a scene depicting an original city that resides on or just above the clouds.

Canvas Size - Max 175 x 225 (either horizontal or vertical).
Colours - Max 25.
Transparency - Optional.
Animation - Optional.