Entire families cross on foot from Panama into Costa Rica to a makeshift migrant camp at a former airfield in Paso Canoas, 300 km south of the capital San Jose, after a long and exhausting journey in the heat. They have survived the natural obstacles of the jungle -- the rivers, torrential rain, treacherous climbs and cliffs -- but also the criminal gangs who often rob, kidnap or rape them. Most are headed to the US and, they hope, a better life. IMAGES AND SOUNDBITES