Mexico border wall at Tijuana, Baja California: What it's like to cross the border from San Diego, USA into Tijuana, Mexico

It's the biggest land port of entry in the western hemisphere.

To the south, a gargantuan cluster of cars and buses in a 10-lane-plus bottleneck head north towards the US town of San Diego.

Passengers could be kept waiting for hours to cross into the border into the US.

Yet heading south into Tijuana, it is very easy to cross the border into Mexico. A 30 minute tram ride takes you from downtown San Diego to the border at San Ysidro where it's a quick interview, a stamp on the passport and you're in.

Across the other side, touts sell tacos and taxi rides for US dollars as you cross the pedestrian bridge which overlooks the lines that snake back into the US, full of both Americans and Mexicans who found a cheaper way of living in Tijuana but still cross daily to earn US dollars in San Diego.

The US and Mexico have had a long history of living closely together, with many crossing the border to good-time girl Tijuana – first during America's prohibition era, later, sailors, cheap holidaymakers and under 21s.

Tijuana's main street – Revolucion – is lined with bars, clubs, and souvenir stands that once catered to these people, fuelling the local economy.

In 2008, all this changed when drug-related violence hit Tijuana hard, and the once busy streets of Tijuana emptied as American tourists no longer believed it was safe. They also lost the sailors from San Diego's Navy base, who were forced to take their recreational drinking breaks elsewhere.