San Giovanni a Mare, popularly also known as San Giuseppe, the Church standing in the centre of Gaeta turned on to the port via Bosan. The current Church building stands on the site of a small ancient chapel, which was destroyed during the earthquake 1213 year. Between the 15th and 17th centuries San Giovanni a Mare was decorated with frescoes and plaster decorations in the Baroque style (stucco). At the same time in the Church there was a marble main altar and small altars made of artificial marble. At the end of the 19th century the Church was gifted a small cell body of the Neapolitan school, which, unfortunately, in the 70-ies of the 20th century was lost.

In the 20th century the building of San Giovanni a Mare several times reconstructed. Major restoration work was carried out in 1928, the year when they were removed all Baroque decorations. And since 1998-the year until the beginning of the 21st century, work was done to strengthen the building structure.

Simple gable facade of the Church is crowned by a small bell tower with three arches, which contain the same number of bells. In the center of the facade you can see a small round window of the socket, which is located under the portal with frescoed Gothic lunette. While the right side of the Church is inscribed in a residential area, the left part and the apse facing the small pedestrian area. The left side of the original dome of San Giovanni a Mare, decorated with small hanging arches and beautiful mosaics, reminiscent of Byzantine. From the rear platform of the Church you can see three of her apse.

Inside, the Church consists of three naves, the center of which is a transept with a dome. In the depths of each of the nave is the apse: the largest is the main altar, the lining of which is made of Christian reliefs of the sarcophagus 2-3rd centuries. You should pay attention to strong sloping floor covering, made to avoid flooding of the presbytery during high tides. On the walls of San Giovanni a Mare preserved fragments of frescoes from the 15th century.