Lom Janičův vrch, Natural monument in Mikulov, Czech Republic.

Lom Janičův vrch is a flooded limestone quarry beside Mariánský mlýn near Mikulov, an elongated oval pit whose walls expose Upper Jurassic limestone over 150 million years old. Its floor holds a natural lake that formed in 2005 when quarrying ended.

Limestone was quarried here on the site of the former Janičův vrch hill until mining ended, after which a lake formed in the pit in 2005. On 1 May 2014 the Pálava Protected Landscape Area administration declared the 4.06 ha flooded quarry a natural monument, protecting its rock walls, wetlands and Upper Jurassic fossils.

The quarry takes its name from Janičův vrch, the hill that once stood here before limestone extraction removed it. Since 2020 the Pálava PLA administration has limited summer access to 100 people at a time, with an entry fee during opening hours. The flooded pit is a popular natural swimming spot.

The quarry lies next to Mariánský mlýn in the centre of Mikulov's cadastral area. Since 2020, entry during the summer season is charged and capped at 100 people at a time, so arrive early. The water is clearest in spring, before summer crowds reduce visibility.

The upper Jurassic limestone in the quarry walls holds fossils of marine life from a shallow, warm sea more than 150 million years old. The site is protected partly as a palaeontological locality, so the rock faces are the reason for its status.