Learn GIMP from the master.

I'm going to start with these pictures:

We'll start by taking some walls and correcting the perspective with the unified transform tool. Remember to save.

We can now paste pieces of our perspective-corrected wall to the towers. Remember to save.

After merging some layers I add a mask so I can erase and uncover the layer as I please, by painting black or white. Remember to save.

I adjust the lightness and color temperature of the sun-facing walls. Remember to save.

Finally, using the same tools as before, I add the sign. Remember to save.

now go make me proud

Remember to save.