Kasi is famous for its galis (on a lighter note, for its gaalis too). The galis of Kasi are alleyways formed due to the apparently unplanned construction of densely packed houses, mainly in the old quarter of the city. So, there are broad, narrow, stepped, branching etc. galis and there are many blind alleys too. Due to their unplanned nature, galis have no universally accepted standard size, length, material used in paving etc. Galis are found in other cities too, but my knowledge is limited only to Kasi.
The Municipal Corporation has been controlling construction of houses in its own manner and galis are not changing shape now-a-days (this is not my knowledge but my guess). The shape and height of the rooftops is a different case altogether.
In the image above, one can see the very complicated manner in which the rooftops are arranged spatially. The image does not change over time, otherwise the picture will be even more complicated. Over the time the height of the buildings has generally increased. One easily observable fact that proves it is that once upon a time, from the same vantage point and in the same direction, one could actually see the stream of Gangaji. Not anymore.
I remember that there used to be a series of rooftops that I could conveniently pass from one to another, starting from mine. I remember six rooftops accessible from mine and five from any house in the row opposite ours. This came handy specially in the season of kites, i.e. winter leading to khichri or Makar Sankranti. Today, from my rooftop, I can only go to my neighbouring one on one side. No other options are open anymore. Thus the change in construction also means a change in celebration of festivals.
Once upon a time (not so long ago) we used to celebrate so many festivals together, especially using rooftops as community space. We try to do so even today, like the good old days; despite the heavy emigration (brain escape?) of the recent generations. The image below shows people from two houses coming to their rooftops to celebrate Diwali together.
Not only Diwali, Holi and Makar Sankranti were celebrated on the rooftops and in the galis too. The spirit of these festivals was the celebration of togetherness of the individual with his family and neighbours. Special occasions or day to day life, in every part of the communal life, the rooftops used to play their part, and that was not a very long time ago. Birthday, thread ceremony and marriage parties were arranged on the rooftops, with the preparation of food items on one and the serving of the food on the adjoining one.