Usage:
1. Use click and hold to pan the map in any direction.
2. Use the "+" to zoom in, "-" to zoom out.
3.
Single-click at any spot to see the coordinates of that location (latitude-longitude).
4. Use the layers control at top-right to switch between
• "Interwar" -- a 1930's Polish Map
• "Open Street Map" -- a modern, international mapping project
• "Google Road Map"
• "Google Satellite"
5. To return the map to the default view, refresh the web page.