There are some implausible "origin" stories regarding Isola Tiber, the only island within the boundaries of Rome. One tale says that when the Romans drove out their last king they took all the grain from his estates and chucked it into the river, where it formed an island. Eh, probably not. The first thing revolutionary mobs generally do is confiscate wealth, not throw it away.
A more amusing if only slightly less believable story involves ships and snakes.
The year was 292 BC. A plague was festering in the city. It was decided that Rome needed a temple to Aesculapius, the Greek god of healing. A ship was dispatched to Epidaurus where this cult had its main temple. A statue of the god was obtained and for good measure a large snake - sacred to Aesculapius - was taken on board.
On arrival in Rome there was a debate as to where the new temple should be established. The decision was finally made by the snake, who slithered off the ship, swam the narrow channel to Tiber Island and curled up in a comfy spot. This became the site of the Temple to Aesculapius, and the start of the 23 century long association of the island with the healing arts. Practically speaking it also made sense to keep sick people on an island with limited access, for quarantine reasons for instance.
Because the island is roughly shaped like a ship the legend became the substance. Here is the downstream side of Tiber Island with the original Roman stonework reproducing the end of a trireme!
I like the orange life preservers up above. Helpful hint, don't try to swim in the Tiber. It looks nasty and the current would pull you under long before help could arrive. If you look closely at the ship-shape above you will see....
The serpent of Aesculapius, in the form of a caduceus, then as now symbol of the healing arts.
The portico outside the temple seems to have served as a place to care for the sick, a function that continued after the repudiation of paganism in the late Empire. In the 10th century a Christian Church was build on the site, initially dedicated to St. Adalbert of Prague. In 1180 it was rededicated and renamed after receiving some more upscale relics, those of St. Bartholomew the Apostle. Because said relics include a rather large piece of the saint's skin, the hospital that continued on at the site developed something of a reputation in the medieval era as being especially adept at healing maladies of this sort. In the 12th century English pilgrim named Rahere fell ill when in Rome, and based on his recovery at St. Bartholomew's returned to England and founded the still extant Hospital of the same name in London.
The basilica of St. Bartholomew has been damaged and repaired quite a few times in its long history, but traces of the earlier ages persist. Many of the marble columns are reused from Roman times, presumably having served in the Temple. And on the steps leading up to the main altar is a 10th century well head. It is said to be on the site of the spring that existed in the Temple of Aesculapius. Also to mark the spot where the snake curled up. I looked down in there and did not see him, but those metal bars over the top must be there for some reason...
The themes of holiness and health still exist today, the northern half of the island is still an active hospital. One day when we walked past a little procession came out of its doors. Darkly dressed morticians carried a casket. A doctor saw them to the door. A priest walked alongside. Japanese tourists snapped pictures.
There is some debate as to how much the island was actually engineered to look like the ship of legend. There was probably a ship's prow at the upstream end. But the small obelisk that once stood in front of the Temple probably was not intended to represent a mast. The surviving fragments of the obelisk suggest it may have been a late Roman imitation rather than an Egyptian original.
The obelisk broke and fell in the Middle ages. It was replaced by a simple column, possibly from the temple, with a cross atop it. Every year on August 24th a list would be posted on this colonna infama of all the local citizens who had not fulfilled their obligation to attend Mass and give confession at least once a year.
In 1867 this tradition came to an end when someone ran into the column with a carriage and knocked it down. It was replaced with the current monument featuring four saints each looking in a different direction. Note the sturdy protective stonework at the base. No chances are being taken on one of the infrequent motorists on the island getting frisky.
This "looking all ways" monument has a famous counterpart not far away. Next time we will pay a visit and will look into some of the odd corners of the Island, places that don't get many visitors.
And advance warning to my fellow Vindolanda excavators.......prepare for a shock.
Addendum. A well done survey of the Tiber Island sites can be found here. The author is conversant with a variety of source material that is not widely available and is of course mostly in Italian.