The Parliament building, located in the southwestern part of Syntagma Square, holds a special place in Greek history, as the House of Revolutionary Greece housed it.

It dates back to 1730, during the Second Turkish occupation of the city, and was originally built as a mosque. It is built with the system of economic masonry carving and consists of a square room covered with a large dome. It is a characteristic mosque of mature Ottoman architecture with its heavy proportions and massive dome. To the west, there was an original dome with a dome, which fell in the early 20th century after an earthquake.

According to local tradition, this large mosque was built by a wealthy Turkish agha to save his soul from a heinous crime he had committed. Agas had killed two young men from Venice who had come to Nafplio to search for the treasure their father had concealed when the Venetians occupied the city. Agas found the treasure, according to the profile of the young men, but killed them in order to reap the spoils himself. Later, feeling remorse for his abominable deed, he is said to have built with the gold of the treasure the large mosque of the square, which became known as the Aga Pasha Mosque.

After the liberation of the city, this mosque housed the Greek Parliament from the autumn of 1825 until the spring of 1826, after it was first properly designed by the architect Ballianos. This was also its most important use and has been known to this day as Parliamentary.

Like other major buildings in the city, it has been used over time for a variety of purposes. In 1831 the Greek School operated for a short time, while its ground floor served as a prison. During the Kapodistrian and Otto period of Nafplio, from 1828 to 1834, municipal dances were usually given here. In 1834, during the Reign, the Trial of the chieftains of the Greek Revolution, Theodoros Kolokotronis and Dimitrios Plapouta, took place.

Today the Parliament has been exemplary renovated by the Ministry of Culture and serves as a conference room, where in addition to conferences many other cultural events are held.

On the ground floor of the Parliament, the Municipal Art Gallery of Nafplio was recently relocated with an interesting collection of paintings by contemporary Greek and Greek artists. The works are mainly donated by the Rotary Club of Nafplio and Nafplio Nikolaos Karagiannis.