Upper Mlynská dolina – Železná studienka – is among the most famous Bratislava recreational sites. It is part of Bratislava Forest Park, which is managed by the city organization Mestké lesy on the behalf of the city. It is located on the southern edge of the protected area of Malé Karpaty.
Vydrica stream flows through the area and its middle flow supplies water to four ponds. Near the main flow are smaller springs, wells and waterlogged areas.
Very special feature of Železná studienka is the harmony of technical buildings (mills, ponds, forestry and fisheries facilities) with leisure-time buildings popular among people. Železná studienka had been populated centuries ago with millers settling there who build the mills. Water mills, already mentioned in 1455, ceased to exist in the late 19th century and served as restaurants. They served as an end point for walks leading from Hlboká cesta, Calvary, Horský park, Patrónka up to the Červený most. From these mills only the ninth was preserved – Suchý mlyn. Klepáč, originally the seventh mill, ceased to exist prior to 1970 and today it is recreational site. An interesting technical monument is a system of four lakes built in 1846 to power nine Vydrica mills. The lakes are currently used for fishing. City wants to use them for boating.
Železná studienka was named after the spring rich in iron which springs up there. Soon it became a spa of King Ferdinand and rumors about the medicinal effects of the spring lured visitors from afar. Pressburg business people seized the chance and built a bathhouse with a restaurant that was demolished in the seventies of the last century. After the analysis of water between 1826 and 1857 it was found that water was not mineral. Baths Železná studienka disappeared and became a popular destination of nearby Pressburg residents.
Železná studienka railway station is located near the Červený most in the valley of Vydrica river. It is part of the track on which on 20th August 1848 came to Bratislava the first train pulled by steam engine from Vienna. The track helped to develop the first railways in Slovakia and connected Bratislava with all future railway system in Europe.