Rhyta are pouring vessels. The object which this is a replica of would have been filled with wine, which would then pour out of a hole at the mouth.
The bull’s head rhyton discovered during the excavation of the Little Palace at Knossos has become one of the most famous objects found at Knossos on the island of Crete. Archaeologist Sir Arthur Evans, the excavator of Knossos, was not allowed to remove the original from Crete and so commissioned this plaster replica. It was included in an exhibition at the Royal Academy in 1936 where replicas stood in for objects which remained in Cretan museums.
Further reading
Athanasaki, Katerina. ‘Replica of Bull’s Head Rhyton’, in A. Shapland (ed.), Labyrinth: Knossos, Myth & Reality (Oxford: Ashmolean Museum), p. 156-7.