Gradierwerk Bad Reichenhall, Evaporation tower in Bad Reichenhall, Germany.

The Gradierwerk Bad Reichenhall is a wooden tower in Bad Reichenhall, Bavaria, built with a lattice of blackthorn branches through which salt water slowly trickles down. As the water flows, it evaporates and releases salt minerals into the surrounding air.

The present Gradierhaus was built in 1909–1910 to plans by Eugen Drollinger, replacing earlier graduation works on the site. Bad Reichenhall's first brine-evaporation attempt dates to 1615; a 1758 structure measured 160 metres, and an 1848 rebuild reached 720 metres. From 1846 guests used the neighbouring graduation works as an open-air inhalatorium, and most were demolished between 1869 and 1888, leaving a 170-metre section for spa use.

Since 1846, guests at the Achselmannstein spa have used Reichenhall's graduation walls as an open-air inhalatorium, breathing the salt-laden air. The present house, planned by Eugen Drollinger, was built in 1910 purely for this purpose. Guided tours from April to October explain the old technique in the attic.

Paths around the tower are open to walkers at any time of day and require no special preparation. Spending around 30 minutes to an hour near the structure is generally enough to notice the salt-rich air it produces.

Although the tower stands deep in the Alps, the evaporating salt water creates a microclimate that feels similar to seaside air. The blackthorn branches filling the frame are replaced on a regular basis, as they gradually become encrusted with salt crystals and lose their effectiveness.