Onezhsky Krestny Monastery, Orthodox monastery on Kiy Island, Russia

Onezhsky Krestny Monastery stands on Kiy Island in the White Sea, founded in 1656 by Patriarch Nikon. Its stone Cathedral of the Exaltation of the Cross, built under master Averky Mokeyev and consecrated by Nikon in 1660, sits on the island's highest point, topped by a single cupola on an octagonal drum. Nearby are the 1660 Over-the-Well Church, the 1689 Church of the Nativity of the Theotokos with its bell tower and refectory, and the wooden Church of All Saints.

Nikon survived a storm near Kiy Island in 1639 and set up a votive cross there. In 1652, as Metropolitan of Novgorod, he revisited the island and renewed his vow. In 1656, by a charter of Tsar Alexei Mikhailovich, he founded the monastery as a stavropegic (patriarchal) house, partly to counter the Old Believer influence of Solovki. It was closed in 1923.

The monastery's most venerated relic was the Kiy Cross, a cypress cross made for Nikon to match the dimensions of the Cross of Christ, holding relics of about 300 saints. It is now in Moscow's Church of St. Sergius of Radonezh in Krapivniki. The monastery also kept Nikon's wooden staff and a turned candlestick, and a 250-leaf life of the patriarch written by his stavrophore Ivan Shusherin.

The monastery stands on Kiy Island in Onega Bay, reachable by boat from Onega; the crossing is open in the ice-free season. The complex is closed and not maintained as a museum, so check locally before travelling. The rocky terrain and unpaved paths make sturdy footwear advisable.

The monastery's most venerated relic, the Kiy Cross, was a cypress cross commissioned by Nikon to match the dimensions of the Cross of Christ. It held relics of about 300 saints and pieces of holy land. In 1991 it was placed in the Church of St. Sergius of Radonezh in Moscow, not on the island.