At the northern point of Menorca, near the Cap de Cavalleria, lie what remains of the Roman city of Sanisera. Nowadays, little is left of this two millennium old city, but excavations are ongoing and archeological finds continue to turn up.
If you go expecting Pompeii, then you'll be disappointed. If you go expecting a number of ancient foundations and a handful of standing constructs (like Martello Tower), then you'll be happy, especially when combining it with hikes or tours around the beautiful Cap de Cavalleria. For more information and a chance to view some artifacts, visit the ecomuseum at Cap de Cavalleria.