Italy, Denmark and Finland have called for Spain to be blocked out of the EU's visa-free Schengen travel zone after the Spanish enclave of Ceuta in Morocco was overwhelmed this week by the arrival of 60,000 migrants
But is such a call, supported by some governments and political figures in Europe, even possible?
READ ALSO: Spain says 60,000 migrants stormed Ceuta but 20,000 have returned to Morocco
What is the Schengen zone?
It is one of the European Union's most tangible achievements -- a border-free travel area in which checks have been abolished for travellers.
