Rtanj (Serbian: Ртањ pronounced [r̩̂ːtaɲ], Romanian: Artan) is a mountain situated in eastern Serbia, approximately 200 km southeast of Belgrade, between the towns of Boljevac on north and Sokobanja on the south.

The north side of the mountain is covered with forests and shrubs, full of autochthonous plant species and plenty of sources of potable water.

Some 1,000 miners participated in the construction as Minh, in the process of developing the mine, built apartments, school, community health center, cinema, park, etc.

In an effort to find the gold and jewels which according to the folk mythology were hidden inside the mountain, the treasure hunters damaged the chapel using dynamite on several occasions since the 1980s, demolishing the remaining walls in the process.

[5] The most popular theory is that, due to its shape and other "observed" factors (precise pyramidal geometry, golden ratio math, wondrous natural life, strong electromagnetism with fine frequencies, endemic plants, healthy energy radiation, special climate, mystical cultural heritage, naturally radiation-ionized air, Tesla waves), the mountain had to be artificially built.

Claims are made that it is a multi-dimensional portal, that a channel leads from the top of the mountain to below the ground being used as a launch pad for alien spaceships and that Rtanj is an "oscillator and resonator of the subtle energy hubs".

Many people have flocked here prior to the predicted 2012 Mayan Doomsday, believing it will protect them,[5][6] as Rtanj is the "strongest energy spot on the planet".

[5] Before it gained its modern reputation, it has been used by the local population as a remedy for bronchitis, asthma, coughing, children's respiratory inflammations, and gerontology problems.

[2] By May 2019, the massive summer harvesting of winter savory on Rtanj was banned by the Institute for Nature Conservation of Serbia until the species recovers.

[2] Medicinal and aromatic wildly grown herbs picked on the Rtanj and the mountain Ozren, which is on the opposite, southern side of Sokobanja, account for the majority of the Serbian export of these commodities, which in 2018 reached €3.3 million.