The core concept is to display each level of the geographical hierarchy in a different layer. Each layer would use a different chart type. In our example we'll use bubble chart type for State/Province and column bar for City. Our source data is SQL Saturday 2012 Oklahoma City registrations by State and City. The result will be the following:
GeoFlow: SQL Saturday Oklahoma City 2012 Registrations by State and by City
The bubble chart type represents the State data, and the column bars represent data by City.
1) Select City and State for the Geography and click Map It
2) Click the check boxes for Attendee Type, Registration Count and Date Added. Chart Type of Column should default, if not, change the chart type to Column.
3) Rename the first layer to Registration by City
4) Click the Add Layer button in the ribbon. This layer will display data at the State/Province layer, thus, allowing us to see data at that level of the geographical hierarchy, as well.
5) Select State and click Map It
6) Click the check boxes for Registration Count and Date Added
7) Change Chart Type to Bubble
8) Remove the Layer's legend and rename the layer to Registration by State
For those interested, below are screenshots of the same data in PowerView.
PowerView: SQL Saturday Oklahoma City 2012 Registrations by State
PowerView: SQL Saturday Oklahoma City 2012 Registrations by Cities in Oklahoma (drilled down from Oklahoma)
While PowerView provides drill down capability via geographical hierarchy, using multiple layers allows us to display both levels of the hierarchy simultaneously within GeoFlow.
Update (tip from @mssqlgirl): In GeoFlow, if you have selected multiple geography fields, like City and State, within a layer, you can use the below option to switch back and forth between the geographical hierarchy levels, while in "Design" mode. I've yet to find a way to do this within "Play" mode for a tour.