Megyer-hegyi Tarn

The Megyer-hegyi tengerszem and its surroundings is a unique former millstone quarry in the management of the Aggtelek National Park, a site of great importance in mining history and geology, as well as a botanical and zoological relic formed since the end of mining, a protected area in Károlyfalva, Borsod-Abaúj-Zemplén County.

Geography and tourism

The lake is located on the 324‑metre‑high Megyer‑hegy above the city of Sárospatak. Although its name contains tengerszem, it is actually a mining lake whose water is rainwater, unrelated to the glacial water of tengerszemes. The main mass of the hill is well workable and solid, consisting of over‑turned Upper Miocene rhyolitic tuff formed in the Cenozoic era. Its depth can reach 6.5 metres in places, and the surrounding rock walls rise up to 70 metres above the water surface. The mine pit is only 4000 cubic metres.

Today the lake is a popular hiking and excursion site, as well as a geological exhibit and cultural‑historical presentation place, where well‑maintained trails for tourists are available and information boards also aid orientation. It can be approached on foot from Károlyfalva and Sárospatak via tourist paths.

The Malomkő educational trail has a high visitation rate, marked with a red hiking sign leading from the centre of Sárospatak. In the forest the signs are clearly visible, however the terrain is quite steep, but it is worth undertaking, as railings make it safe for those who wish to look into the water‑filled basin from above – the former mine edge. The length of the trails is about 1 km.

In 2011, in the online game *Csillagtúra* of the Origo internet newspaper, which searches for Hungary’s 7 natural wonders, readers voted the Megyer‑hegyi tengerszem as the most beautiful and ranked it first.

Origin and history

The 324‑metre‑high Megyer‑hegy is a volcanic rhyolitic tuff cone from the middle Miocene of the geological third period, its mass being built mainly of horzstone‑cobble rhyolitic tuff and hydroquartz.

The rock impregnated with acid after solidification is characterized by very high hardness, which its crystalline veins and cavities made ideally suitable for millstone production. People mined the millstones for grain grinders and ore crushers here from as early as the 15th century. The miners cut small chambers for themselves in the wall of the mine and also lived there. The shaping and finishing of the millstones were carried out for several centuries with almost the same techniques, tools and manual labor.

In the former mining pit, a significant amount of rainwater has accumulated over time. Thus a permanent water lake, still present today, was formed, with a total volume of 4000 cubic metres and a deepest point of 6.5 metres. During the mining period, drainage channels were also constructed to remove the accumulated water.

The mine was closed in 1907 due to a continuous decline in production. In the former quarry yard, a few partially finished millstones as well as by‑products of stone‑cutting activity can still be seen today.

Conservation

The lake and its surroundings were declared a nature reserve in 1997, whose full name is: Megyer-hegyi Tengerszem Nature Reserve. Its aim is to preserve the specific botanical, zoological and geological values of the spring pond formed by the accumulation of rainwater.

Area 1.07 hectares, freely accessible all year round. Managed by the Administration of the Aggtelek National Park. The park is one of the smallest such protected areas in Hungary.