Zálesí, formerly Werlsgrün or Wörlsgrün, is considered the oldest inhabited site in the Jáchymov region. The Renaissance chronicler Johannes Mathesius already mentioned Werlsgrün as an ancient settlement existing even before the foundation of Jáchymov. Its origin is therefore probably connected with the early 13th-century colonisation activities of the Premonstratensian monastery at Teplá.

Werlsgrün was one of the highest and northernmost settlements in the area. By 1386 it is already recorded as abandoned, similarly to nearby Konradsgrün or Hagenau, most likely because of the harsh climate and unfavourable altitude for agriculture.

The site was resettled only after the foundation of the mining town of Jáchymov in the 16th century. Together with nearby Mariánská (Maria Sorg), it provided agricultural support for the mining town, particularly livestock breeding. Further development was linked to the neighbouring silver mine Eva Apfelbaum, one of the significant mines of the region in the 16th century.

In 1847 the settlement had 13 houses with 98 inhabitants, and in 1850 Werlsgrün became an official part of Jáchymov. After the mine closed, the inhabitants returned to livestock breeding, grazing and forestry work. In 1930, 69 permanent residents still lived here.

Major changes followed the Second World War. In 1948 the settlement was officially renamed Zálesí. In 1961 it became a local part of Jáchymov and remained so until its disappearance on 1 January 1974. Only a single house and a few garden cottages survive today.

Uranium mining dealt the decisive blow to settlement in the area. The Eva mine was reopened and the Adam mine was established at the site of the older Ochsenbusch workings. Together with the Eliáš mine they formed a large industrial complex that transformed the entire Eliáš valley.

After uranium mining ended, the buildings stood unused for some time. As part of efforts to remove traces of former prison facilities, the abandoned complex was transferred to the district authority in Most, which established an outdoor school there. Workshops were converted into classrooms, a gymnasium was created from the engine house above the shaft, and former barracks became dormitories, a kitchen and a dining hall. The school operated into the early 1990s; afterwards the buildings were abandoned and today only their remains survive.