US President Donald Trump is today due to inspect eight prototypes for his proposed border wall with Mexico.
They have been built within sight of the current fence marking the international border between San Diego and Tijuana.
Tijuana is a popular destination for immigrants seeking a better life in the United States.
Since taking office, Mr Trump has said the wall will initially need US funding but that he will find a way to make Mexico ultimately pay for it.
Mexico has flatly rejected paying for the wall, which experts have suggested could cost over $20bn and take more than three years to complete.
Six US companies built the prototypes, most from reinforced concrete and the remainder from other material.
The mock-ups are assessed for their anti-breaching, anti-climbing and anti-digging capabilities.
Each prototype section cost more than $300,000.
During the presidential election campaign, Mr Trump's supporters cheered when he loudly promised a barrier along the 3,200km US-Mexico frontier to keep out drug smugglers and undocumented immigrants.