Sanisera was one of the Roman cities located in the island of Menorca, which was mentioned by Pliny the Elder in his book Naturalis Historia, III, 77–78 in the 1st century BC:
The Baleares, so formidable in war with their slingers, have received from the Greeks the name of Gymnasiæ. The larger island is 100 miles in length, and 475 in circumference. It has the following towns; Palma and Pollentia, enjoying the rights of Roman citizens, Cinium and Tucis, with Latin rights; and Bocchorum was a federate town. At thirty miles' distance is the smaller island, 40 miles in length, and 150 in circumference; it contains the states of Jamnon, Sanisera, and Magon.
Wikipedia https://en.wikipedia.org/wiki/Sanisera
Address 07748, Spain
Coordinates 40°4'10.569" N 4°5'15.216" E