The U Mariánské mlýna quarry, also called Na Janičově vrchu, is an abandoned and flooded limestone quarry near the village of Mikulov in Moravia behind Svatý kopeček, in the Pálava protected landscape area.

In the middle of the 20th century, a limestone hill called Janičův vrch stood on the site of today's flooded quarry near Mikulov, rising to a height of 322 m above sea level. nm Since 2005, limestone has not been mined anywhere in Pálava.

The local place resembles not only the appearance, but also the climate of the rocky Croatian beach. Fossils can be found in the local limestones. The water in the quarry is crystal clear thanks to the limestone. The rocky beach is connected to a shoal several meters long, which suddenly goes to great depths. However, it is not yet known exactly how deep the lake is.

The excavated limestone quarry is managed by the Pálava Protected Landscape Area Administration. This is not an official public swimming pool, but a tolerated occasional bathing place at your own risk. Occasional bathing by local residents is considered an appropriate level of usability. However, mass recreation would lead the Pálava Protected Landscape Area Administration to close this quarry with a bathing ban.

There is a road passing around the quarry, lined with a blue tourist sign, which passes from Mikulov over Svatý kopeček. The flooded limestone quarry near Mariánské mlýn and its immediate surroundings have been a natural monument called the Janičův vrch Quarry since May 2014.