Lávový proud u Meziny, Natural monument in Mezina, Czech Republic

Lávový proud u Meziny is a 1.22-hectare natural monument protecting a former wall quarry about 1 km northeast of the summit of Venušina sopka. Its face exposes plagioclase basalt columns up to several decimetres across, mostly hexagonal and occasionally pentagonal, with well-developed columnar and spherical jointing.

The lava flow beneath Venušina sopka cooled about 1.8 million years ago, in the lower Pleistocene, leaving columnar and spherical jointing in plagioclase basalt. The former wall quarry was declared a natural monument in 1997, covering 1.22 ha and managed by the Moravian-Silesian regional authority.

The quarry face is called the "stone organ" for its basalt columns, and the local educational trail Po vulkanitech ("Over the Volcanics") links the site with the summit of Venuše volcano and the village of Mezina. The rock is a nepheline basanite with olivine crystals visible in the columns.

The best way to reach the site is by following a walking trail from Venus Mountain through Mezina village, with the monument about 400 meters from the bus stop. The area is accessible on foot and does not require specialized equipment.

The columns are mostly hexagonal, but five-sided sections also occur. The rock is a nepheline basanite with abundant olivine crystals, and the site lies about 1 km northeast of the summit of Venušina sopka.