The 270 meters long island has been inhabited since the Ancient Rome era and has always been connected to the rest of the city by two bridges.
In the third century BC a Temple of Aesculapius - a Greek God of healing - was built there and ever since the island was connected with healing. Interestingly enough, before the construction of the temple, the island was associated with criminals and negative powers.
The island is still connected with medicine today since there is an active hospital located there which was established in 1584.
If you visit Rome during the summer months, you might want to check the L'isola del Cinema film festival which is traditionally held there.
Wikipedia https://en.wikipedia.org/wiki/Tiber_Island
Coordinates 41°53'26.208" N 12°28'38.441" E