The behaviour should be similar to the border display as district and sub-district.
City border is displayed (red) with district markers
On hover of a district the district border is getting displayed in red and the city border displayed in grey
On selection of a district or a filtering below ( post code or sub district) the city border is not visible
Example of the greying out and displaying of a subpart from district->sub-district
krausweb
commented
4 years ago
Use this geo data to display the city border when the map gets opened ( before any selection/filtering of district, post code etc.)
https://geoportal.stadt-koeln.de/arcgis/rest/services/Stadtgebiet/MapServer/0/query?where=objectid+is+not+null&text=&objectIds=&time=&geometry=&geometryType=esriGeometryEnvelope&inSR=&spatialRel=esriSpatialRelIntersects&relationParam=&outFields=*&returnGeometry=true&returnTrueCurves=false&maxAllowableOffset=&geometryPrecision=&outSR=4326&returnIdsOnly=false&returnCountOnly=false&orderByFields=&groupByFieldsForStatistics=&outStatistics=&returnZ=false&returnM=false&gdbVersion=&returnDistinctValues=false&resultOffset=&resultRecordCount=&f=pjson
The behaviour should be similar to the border display as district and sub-district.