Comment by brightsize

I think a heatmap would look good here, one with nice flowing color gradients, maybe with a separate marker layer over the top. Leaflet-DVF looks pretty promising for that sort of thing and it comes with nifty markers. Of course a cute marker icon that looked like a rat would be good too. I'd prefer to see the building/address info displayed in a marker pop-up rather than on the left. Map apps are fun, I've made a bunch myself with Leaflet.