In fact, present-day South Street (Maltese: Triq in-Nofsinhar) was originally known as Strada del Palazzo, since the palace was meant to be built there.

The ceilings of the main corridors were decorated with frescoes by Nicolau Nasoni in 1724, during the magistracy of António Manoel de Vilhena.

[5] In the 1740s, Grand Master Manuel Pinto da Fonseca made extensive alterations to the building and gave it its present configuration.

[14] Parts of the building, including the hall housing the Palace Armoury, were hit by aerial bombardment during World War II, but the damage was subsequently repaired.

[5] The main façade of the Grandmaster's Palace is built in the simple and austere Mannerist style, typical of its architect Cassar.

The façade is asymmetrical due to the extensive alterations carried out to the building over the centuries, and it has heavy rustications at the corners along with an uninterrupted cornice at roof level.

The cycle of wall paintings decorating the upper part of the hall are the work Matteo Perez d'Aleccio and represent various episodes of the Great Siege of Malta.

The coat-of-arms of Grand Master Jean de Valette on the wall recess behind the minstrels gallery was painted by Giuseppe Calì.

In 1818, the British transformed this hall by completely covering the walls with neo-classical architectural features designed by Lieutenant-Colonel George Whitmore.

The arms collection in the Palace Armoury is regarded as one of "the most valuable historic monuments of European culture", despite retaining only a fraction of its original size.

[15] The original hall of the armoury was converted into the meeting place of the Parliament of Malta in 1975–76,[16] and the arms collection was relocated to two former stables at the palace's ground floor, where it remains today.

In 1712 Romano Carapecchia designed the Perellos fountain,[23] originally dominating the courtyard under the loggias,[24][25] but since the British period became hidden from the main view with the Statue of Neptune and a garden landscape in the middle.

[26] The statue was brought to decorate the courtyard, on orders of the British Governor John Gaspard Le Marchant, some time between 1858 and 1864.

[27] Some escutcheons containing the coats of arms of Grand Masters of the Order are found affixed to the wall of one of the corridors of Neptune's Courtyard.

They were retrieved by Governor Sir Arthur Lyon Fremantle in 1897, and were affixed to the courtyard "for their better preservation", as indicated by a marble slab below the coats of arms.