which items were traded?
Animals.
Indo-Roman trade relations
There is evidence of animal trade between Indian Ocean harbours and the Mediterranean. 
who opened trade between india and the mediterranean world The Roman Empire.
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Indo-Roman trade relations [SEP] Trade of exotic animals
There is evidence of animal trade between Indian Ocean harbours and the Mediterranean. This can be seen in the mosaics and frescoes of the remains of Roman villas in Italy. For example, the Villa del Casale has mosaics depicting the capture of animals in India, Indonesia and Africa. The intercontinental trade of animals was one of the sources of wealth for the owners of the villa. In the Ambulacro della Grande Caccia, the hunting and capture of animals is represented in such detail that it is possible to identify the species. There is a scene that shows a technique to distract a tiger with a shimmering ball of glass or mirror in order to take her cubs.