The church of Metamorfosi Sotiros (Transfiguration of Christ) occupies a central place inside Niokastro in Pylos. It was originally built as a mosque during the reign of sultan Murad III (1573-1595). During the second Venetocracy it was turned into a catholic church dedicated to St. Vito. After the re-conquest of the castle by the Ottomans in 1715 it is likely that the building was once again used as a site of muslim worship. In April 1770, during the Orlov revolt, it was turned into a christian orthodox church. The church was used as an ammunition depot by the French troops at Niokastro (1828-1830) and after that, until 1842. It is then that the monument assumed its religious character once more. The church is surrounded by an enclosure on three sides, except for the eastern one, and consists of the main nave and a vestibule. It has a square ground plan and it is built with rubble masonry, dressed in many parts with hewn poros slabs. Blocks were extensively used in the dome, the arches and elsewhere. In the interior, four columns support the upper part of the church and the dome and four arches arranged in a cross shape. The spaces between the arches, the four corner chambers, are covered with small domes. Large windows are opened on all but the eastern side, where they have been walled. The elaborate niche of the muslim mosque (mihrab) was located at the interior of the eastern side, but it is not visible from the outside.