Complex sentence: Visitors to the resort island travel across a long causeway which crosses marshland which was immortalized by 19th century poet Sidney Lanier in' The Marshes of Glynn (1878).
Split into simpler sentences: Visitors to the resort island travel across a long causeway that crosses marshland. This area was immortalized by 19th-century poet Sidney Lanier in' The Marshes of Glynn (1878).