The lady said it was similar to spinach, but if I'm spelling it correctly, then according to google, I think it might be broccoli raab (also spelt rabe or rapini). 

Date taken: 2014-06-30 17:21:59
Location: Cape Town Station, Foreshore, Cape Town, 8001, South Africa
Co-ordinates: -33.922175, 18.425017
Altitude: 12 metres above sea-level
Camera used: Apple iPhone 5
Direction of camera: NNW