1. A method comprising: providing a user interface that displays a map with a user-operable element that is superimposed on the map and has a shape defined by boundaries of the user-operable element; receiving user input that indicates that a region of the map is selected, the selected region of the map being defined by the shape and the boundaries of the user-operable element superimposed on the map; causing the user interface to display first location markers within the selected region defined by the shape and the boundaries of the user-operable element superimposed on the map in response to the user input that indicates that the region of the map is selected, the displayed first location markers appearing inside the boundaries of the user-operable element superimposed on the map, the causing of the user interface to display the location markers being performed by a processor of a machine; receiving further user input to move the user-operable element away from selected region of the map, the moved user-operable element defining an unselected region of the map; and causing the user interface to continue displaying the selected region of the map and the first location markers within the selected region while also displaying the unselected region of the map and second location markers within the unselected region, the unselected region being defined by the boundaries of the moved user-operable element and being colored differently from the selected region, the first location markers in the selected region being colored differently from the second location markers in the unselected region.