There are four larger islands and ten tiny islets . The names of the large islands are Sylt , Föhr , Amrum , and Pellworm . The islets are called '' Halligen '' . In medieval times the present-day peninsula Nordstrand and Pellworm as well as the Halligen were part of the large island of Strand . This island was torn to pieces in a disastrous storm tide in 1634
disastrous storm tide
Burchardi flood
North Frisian Islands