Using CLLocationManager and CLRegion to detect proximity to the Eiffel Tower

EiffelTowerRegionMonitoring.m

CLLocationManager *locationManager = [[CLLocationManager alloc] init];
[locationManager setDelegate:self];
[locationManager setDesiredAccuracy:kCLLocationAccuracyHundredMeters];
[self setLocationManager:locationManager];

// ...

CLLocationCoordinate2D eiffelTowerCoordinates = CLLocationCoordinate2DMake(48.858093, 2.294694);
CLLocationDistance radius = 20; // 20 meters
CLRegion *region = [[CLRegion alloc] initCircularRegionWithCenter:eiffelTowerCoordinates radius:20.0 identifier:@"Eiffel Tower"];

[[self locationManager] startMonitoringForRegion:region];