Demerdji natural boundary, Natural monument in Autonomous Republic of Crimea, Russia.

Demerdji natural boundary covers 20 hectares on the southern slope of Mount Southern Demerdji (1,239.8 m), south of the Demerdji-yayla plateau near the village of Luchistoye. Its Valley of Ghosts is a field of Upper Jurassic conglomerate weathered into pillar shapes up to 25 m tall, with niches, ledges and wide cracks. The best-known formation is the Khoy-Kaya rock, also called the Warrior or Katerina; the Velikan pillar is 5 m across and 25 m high.

The tract was first declared a local nature monument in 1960, then reorganized as a national-level geological monument by decree No. 145 of the Ukrainian SSR Council of Ministers on 30 March 1981. The Alushta state forestry enterprise is the land user of its 20 hectares. A collapse of the South Demerdzhi slope in 1894 sent rock debris down to the village, destroying four houses and prompting the settlement to be moved to the site of present-day Luchistoye; further collapses occurred in 1966 and 1992.

The name Demerdji comes from the Turkic word for blacksmith, and a local legend tells of a smith who forged weapons on the summit until a girl named Maria stopped him; the mountain swallowed the forge and the rocks that resemble figures are said to recall them. The best-known formation, Khoy-Kaya, was renamed "Catherine" in the Russian Empire after Catherine II.

The site is accessible via marked hiking trails that wind through forest areas and across rock formations. Visitors should wear sturdy footwear and be prepared for uneven terrain and variable weather conditions.

The best-known formation is the Khoy-Kaya rock, also called the Warrior or Catherine, renamed after Catherine II in the Russian Empire. The Giant pillar measures 5 m across and 25 m high, ringed by pillars of 10 to 20 m. A 1894 collapse broke off a block that shattered into fragments up to 25 m wide and destroyed four houses in the village below.