The default value is null.
The following example shows how this property can be set to provide 3D imagery:
C# Example
var target = new CLLocationCoordinate2D(37.7952, -122.4028);
var viewPoint = new CLLocationCoordinate2D(37.8009, -122.4100);
//Enable 3D buildings
mapView.ShowsBuildings = true;
mapView.PitchEnabled = true;
var camera = MKMapCamera.CameraLookingAtCenterCoordinate(target, viewPoint, 500);
mapView.Camera = camera;
