Niokastro is built on a low hill at the south entrance of Navarino bay. It is called Niokastro or Neo Navarino in contrast to Palaiokastro or Palaio (old) Navarino (a 13th century Frankish castle) at the north end of the bay. It was founded by the Ottomans in 1573 in order to protect the natural harbour of Navarino and the south-western coast of Messenia. It remained under Ottoman command until the outbreak of the Greek revolution, with a short-lived interval between 1686 and 1715. In 1821 it was liberated by the Greek revolutionaries, but it was captured by Ibrahim Pasha in 1825. Following the battle of Navarino (1827) the castle was surrendered to general Maison’s expeditionary corps in 1828 and its walls and bastions were repaired. In the second half of the 19th century and up to the mid- 20th century the castle housed Pylos’ prison. During World War II it was used by the Italian and German troops.

The fortress consists of the hexagonal acropolis to the east, and the walled-in settlement to the west. The acropolis was built at the highest and most vulnerable point, reinforced with an outer moat and six five-sided bastions. The walls surrounding the settlement are inwardly inclined and crowned by crenellations, accessed via a narrow corridor. They are reinforced by two semicircular bastions, north and south. Worth noting is the south flank wall, called “Megali Verga” (freely “long flank”), where the corridor is supported by a series of barrel-vaulted arches. Two four-sided bastions to the west were protecting the harbour entrance. The main castle entrance was at the east, with the imposing gate named “Zematistra”.