​It is an Orthodox monastery of monks, founded in the 17th century by Voivode Gheorghe Duca. The Cetățuia Monastery dominates the landscape with its slender silhouette, guarded by an imposing tower and surrounded by a stone wall worn by time.

It was built from the beginning as a medieval fortified complex capable of offering the ruler and the boyars a base for armed resistance against the invaders. A printing press with Greek letters, brought from Venice, operated here. Having fallen into ruin at the end of the 19th century, the monastery was restored in the interwar period at the initiative of the historian Nicolae Iorga.

Given the partial demolition, at the behest of the Turks, of the Moldavian fortresses by Alexandru Lăpuşneanu and the prohibition by the Porte to build fortifications, the Moldavian lords were left with the option of using a fortress camouflaged as a monastery to defend themselves. This did not have the value of a true fortified place, but it provided the ruler and his family with an advantage against an enemy. In the past, on the Cetățuia hill that dominates the southern part of Iași, there were vineyards, gardens, orchards or forests. In the summer of 1666, the ruler Gheorghe Duca of Moldavia (1665-1666, 1668-1672 and 1678-1683) bought a large vineyard there from several owners, with the probable intention of building a monastery. Being deposed shortly after, it seems that his plans remained unfinished.

In the autumn of 1668, after his return to the throne, the construction of a fortified monastery began, which was also to fulfill the role of a defensive fortress in the event of invasions of Moldavia. The pace of construction was very brisk, in the spring of 1669 the walls of the church were almost finished and, as is evident from the princely letters that the prince's proxies had received, the purchase of roofing material was sought. As evidenced by the documents and the inscription on the bell tower, on June 10, 1670, the construction of the walls of the enclosure, the bastions and the bell tower had already been completed. However, the consecration of the church took place only in 1672, after the church was painted and endowed with religious objects.

The monastery was dedicated to the Patriarchate of Jerusalem since 1670, when it had not yet been completed. In 1672, Prince Gheorghe Duca buried one of his daughters, Maria, in the new church.

Prince Gheorghe Duca and his successors on the Moldavian throne endowed the monastery with several estates, including the revenues of over 200 buildings in Iași.

Thus, Galata was built and later, the Citadel, as a fortress-monastery, by Prince Gheorghe Duca (completed in 1672). The position of the Citadel is one of the best, being located near the city and the Royal Court, at the highest point in this area and the fortification wall still exists today, except for the western part. The walls are up to 7 meters high and 1.40 meters thick.

The abbess' building is somewhat smaller than the royal palace, consisting of a ground floor and a cellar. The architectural pride of the Citadel is the Gothic hall - the refectory - inspired by the refectory at Dragomirna and at Trei Ierarhi. and which occupies the entire right wing of the building (towards the east). Here you enter from the porch through a door framed in a carved stone frame, with intersecting profiles. This is a hall with a length of almost 16 m and a width of almost 9 m, with a floor of hexagonal bricks. It has six pointed vaults, supported by two strong pilasters, located in the central axis of the room and by carved stone consoles located on the walls. The two columns are made of stone and have an octagonal section; they are decorated in the middle with a Moldavian braided belt. At the bottom, the columns are placed on a square stone base, and at the top, under the square capital, there are four beautifully decorated consoles. On the eight carved stone ribs of the vaults there are decorations in the form of square rosettes. The hall is lit by eight windows that overlook the monastery courtyard. Initially, the Gothic hall was painted in fresco, traces of painting (in which biblical characters and biblical scenes can be distinguished) can still be observed today on the southern and eastern walls. The Gothic hall initially served as a refectory, and in the 1990s a chapel was built here.

In the left wing of the building there are three cylindrically vaulted rooms and a small hall, at the end of which there is a secret staircase that leads directly to the lower floor of the cellar.

The church dedicated to St. Peter and Paul, from Cetățuia, is considered a simplified copy of the Three Hierarchs church.

The bell tower was built in 1670 in the southern part of the monastery, also serving as the entrance to the monastery. The princely courtyard at Cetățuia was a residential palace and also a fortress keep.