The square, semi-rectangular shape, is characterized by the imposing presence of the castle Maschio Angioino on the south side.
On the north side there is a side of the Palace of the Bank of Italy and the INA, the palace of the Grand Hotel de Londres (currently home to the Regional Administrative Court), the palace of the old mail couriers, the Theatre Mercadante.
On the west there is the St. Giacomo Palace, seat of the municipality of Naples, and incorporated in it the basilica of St. Giacomo degli Spagnoli.
Since 2014 in the center of the square, just in front of the Town hall, there is the monumental Fountain of Neptune. The fountain was built by Giovanni Domenico D'Auria using a design by the Swiss architect Domenico Fontana, between 1600 and 1601.
Finally, to the east there is the building of the maritime station, completed in 1936.
On the southwest side, corner of Via Verdi, overlooking the palace of the Bank of Roma.
Stations of Line 1 and Line 6 of the Naples metropolitan are currently under construction, located between the theater and the castle.