Using Map Kit, the portion of the map that is displayed on the screen is
referred to as the region. The region is defined by a center location and
a span of the surrounding area to be displayed. Inside the Map View an
annotation could be created, indication a Point of Interest. In this
tutorial we will display a portion of the city London and we will add an
annotation of the Big Ben. This tutorial is made with Xcode 8.2.1 and built
for iOS 10.2.