I have blogged already how to drill down to another page using Parameter, today, I find another approach, it is extremely easy, and a bit embarrassed why I have not thought about before !!!
I will be using administrative division of Algeria as an example, see the report here, please notice the pattern is not only for maps, personally I use drill down to another page extensively with finance reports, for example drilling down by Project, vendor, user etc
1- Create a map at the region Level
2- Add a new empty tab
3- Make the Map at the report level
4-make sure apply filter is on
5- in the second tab , hide the map either using send to back or add a big rectangle
6- add a new map at the city level
7- add a new button to navigate between page 1 and 2
basically when you create a report level map, the selection from page 1 get synchronized to page 2 , then the hidden map in page 2 will filter the map at the city level.