In 1573, two years after the defeat of the Ottoman fleet at the naval battle of Naupactos (Lepanto), the Turks built the fortress of Pylos, with the aim of controlling the southern entrance to the bay of Navarino, the largest natural harbour in the Peloponnese.
The new fortress was called Niokastro (New Castle), to distinguish it from Palio Navarino (Old Castle), the Frankish castle on the peninsula of Koryphasion, which had controlled the opposite, norhtern entrance to the bay up to this time.
Navarino Bay, is the only large natural harbour on the W coast of the Peloponnese. It is enclosed on the seaward side by the island of Sfaktiria, a huge rocky barrier 4.6 km (3 miles) long and rising to a height of 135m (443 feet)
History: The Mycenaean kingdom of Pylos was conquered by Neleus and thereafter was ruled by his youngest son, Nestor. In 1939 Carl Blegen discovered at Epano Englianos a site belonging to that period.
In the 7th - 6th c. BC. a Dorian settlement named Pylos was established on Mt. Koryphasion at the N end of the bay.
In 425 BC., during the Peloponnesian War, the town was occupied by the Athenians , who also captured the island of Sfaktiria and took its Spartans defenders prisoner.
In the 13th c. AD. the Crusader Nicolas de Saint- Omer built a castle here (Palaiokastro, the "Old Castle"), which was later successively held by Venetians and Turks.
On 20th of October 1827 the allied fleet under the command of three, - the British Admiral Sir Edward Codrington, the French Admiral De Rigny and the Russian Count von Heyde, sailed into Navarino Bay to make a show of strength, but a shot fired by the Turkish and Egyptian fleet unleashed a battle which had not been intended by the allied governments and which ended in the destruction of 58 out of the 87 Turkish vessels.
Their remains can be seen lying on the bottom of the bay when the sea is calm. The battle gave a decisive new impulse to the Greek war of liberation.
In 1686, the Venetian admiral Morosini captured Niokastro after a siege and it was turned into the seat of the Overseer, the Venetian governor of the area. During their period of occupation (1686-1715), the Venetians repaired and strengthened the castle at many points .
In 1715, Niokastro was recaptured by the Turks, who made it the headquarters of the vilaet of Navarino. It remained in Turkish hands until the outbreak of the Greek War of Independence in 1821, apart from a brief interlude of a few months in 1770, when it was captured by the Russian forces under the Orloff brothers.
The castle was surrendered to the Greeks in 1821. At the beginning of 1825, Ibrahim Pasha disembarked in the Peloponnese at the head of Egyptian forces and encamped at Niokastro. The Castle was placed under an asphyxiating siege lasting three months, during which dramatic events unfolded both inside and outside it, ending with the capitulation of the Greeks and the surrender of Niokastro to Ibrahim. A leading role in these events was played by the Greek general Ioannis Makrigiannis, who was left us an elegant account of them. After the victorius outcome of the battle of Navarino in 1827, European doplomacy decided in favour of the creation of an independent Greek state. Niokastro remained in Ibrahim's hands until September 1828, however, when it was surrendered to the French forces of General Maison.
Since 1892, when it devolved upon the Ephorate of Maritime Antiquities some of the rooms have been remodelled (after the excavation and restoration work) to house the Underwater Research Center for Marine Antiquities. The main architectural features of Niokastro, which covers an area of about 19 acres, are the two square bastions on the west-side, which face the sea, the hexagonal citabel at the south-west edge, and the fortification wall, which is reinforced with four round towers and links the individual fortress complexes.