The process is based on aggregating of open data.

The first step was to get apartment building data from the Ministry of Housing and Communal Services and cultural heritage sites data from the Ministry of Culture — then they were elaborated in Excel and geocoded using a Google Sheets extension.

This was not enough, since only a third of the buildings got their data. I used my colleagues' script to get data from Rosreestr (Russian Registry), which was elaborated in Pandas Dataframe afterwards. The dataset consisted of 14 000 points in the end.

All the further and most interesting work was done manually.

First of all, Kaliningrad used to be Königsberg before 1946. If you are a local, you probably know the pecularities of our address system, which keeps the German order. In a nutshell, a lot of houses did not get new numbers after the war, whereas the numbers were given to each entrance door separately (it is not common in Russia where one number is given to the whole building even if it is quite long). 
It is a real challenge for spatial join of points and polygons. The thing is, there are many buildings whose parts were built in different periods. If one part of a building is a Khrushchev's house and another part is an art-nouveau house, this whole object is likely to be shown as one polygon in OSM.

Secondly, sometimes the year of the reconstruction is noted as the year of constructing. However, our map is to show the original year if the building has not been demolished and destroyed.

The next step was to get some extra accurate information. With the help of local historical websites and the regional state archive publications, I managed to add new data about many interesting houses that were ignored by the Ministry of Culture and Rosreestr. Besides, I filled in the style and name fields of some houses manually – mostly what I could find on the Internet – and added some photos from my own photo album.    

Then I had to define historical and architectual periods in order to visualize my data. It turned out to be a mixed structure:

1. The German history starts in 1255 (when the castle construction started) and was divided according to the organization of the state, which was related to architectual changes.
2. The Soviet history was divided according to the periods when this or that leader ruled. This is a common architectual assosiation for Russians.
3. The recent history is divided into decades which are gradually being conceptualized.

Exceptions and notions:

• The "Teutonic Order" and "Duchy of Prussia" periods were merged, since they only consist of 5 objects in total;
• "Weimar Republic" and "Third Reich" were merged, since there is a lack of necessary information for dividing this periods;
• The German Empire and the Weimar Republic periods were sometimes divided manually because the "beginning of the XX century" is a common but ambiguous label which may refer to either period. It was a hard job, as they are separated by the First World War, when the city constructions were impeded and the city development changed significantly. I analyzied old German maps for marking up. Still, there are probably some inaccuracies.
• The Stalinist period is denoted up to 1955 when the resolution "On elimination of excesses in design and construction" was adopted. The houses, which were then restored, got a "pre-war" label. I established the restoration facts comparing the postbellum (implying WWII) maps. 
• The legend ignores Andropov's and Chernenko's ruling for the sake of simplification.

Kaliningrad really has a complex history – you will also see this on the map. 

I made a diagram. It is not accurate because the most German houses got a rounded year in their data. As you can see, the pre-war architecture is still common in the city. Also we should notice two construction booms in 1960s and 2000s. The 1950s look like a complete void, since the city was restoring damaged houses in the non-central german districts. The end of 2010s seems to be a decrease which might be due to lack of recent data.

The advantage of Geosemantica platform is that everyone can suggest edits about years, photos and general description. This way our map will become more accurate and relevant.

Colors were collected out of Kaliningrad's images. The traditional red brick of the northern neo-gothic and clinker bricks of Bauhaus, the dull beige walls of Hufen disctrict – this is what we relate to Königsberg in our minds. The green and light blue shades were referred to the Soviet housing with its recently restored unique decorative panels and notorious House of Soviets. The dark blue tones were taken out of wet cobblestone paving. However, this color was defined for the contemporary architecture with a plethora of glass and metal.

We designed a poster which you can order here