In the southwest corner of the American mainland is the port city of San Diego, one of the major hubs of the US Navy. The city itself is very interesting, with a city centre dominated by colonial-styled buildings. Balboa Park is home to one of the best zoos in North America, and the historic ‘old town’ area north of the city centre has become a popular ‘Old Mexico’ theme attraction. As well, there is the Tijuana Trolley, which is, in fact, a modern surface-rail tram line that goes from the city centre to close to the walk-across border with Mexico into colourful downtown Tijuana. A day visit to Mexico is one of the highlights of a visit to San Diego!