A Schengen visa valid for Greece, covering the travel dates and retaining the necessary entry and stay allowance can generally satisfy the visa requirement without a separate island application. However, checking only the expiry date is insufficient. Review territorial validity, whether the visa permits single or multiple entries, previous use and the remaining stay allowance. A single-entry visa already used for a completed visit may not support another entry even while its printed validity period continues. The visa also does not remove border-entry conditions. Carry the relevant passport and travel evidence, and ask the competent Greek authority about any restriction or uncertainty.