Based on my own understanding of the Genesis, the garden of Eden was situated on the first heaven made on the 2nd day - surrounded by midst of waters above and below it - which was completely destroyed by the universal flood during the time of Noah.
I believe, there were numerous worlds made during the creation process:
Gen. 1:6-8 documents that the 1st Firmament or Heaven was made on the 2nd Day - Garden of Eden.
Gen. 2:4-5 documents that the 2nd (our world) and 3rd Heavens were made on the 3rd Day (New Jerusalem).
IOW, Scripture documents that there are 3 Heavens (kosmos or worlds) -- Read ll Peter 3:5-7 which explain how God spoke of the world that THEN WAS, being overflowed with water, Perished. (Greek-Destroyed, Totally). Our present world were made on the 3rd day. Revelation 21:1-2 document us another world (New Jerusalem) where all Christians will live when this present world is totally destroyed by fire as prophecied in the Scripture.
Just my humble opinion based on the Scripture.
God Bless