Navadvipa are nine (nava) mystical islands (dvipa), today’s Mayapur in West Bengal. Navadvipa is connected with Chaitanya, Mayapur is the main place of worship.
He was born on the island Antardvipa. The other islands are Simantadvipa, Godrumadvipa, Madhyadvipa, Koladvipa, Ritudvipa, Jahnudvipa, Modadrumadvipa, Rudradvipa.
Read about Navadvipa here
https://www.holydham.com/navadvipa-dham/