Trojská, Natural monument in Troja district, Prague, Czech Republic

Trojská is a 1.27-hectare natural monument on a southeast-facing slope between Trojská and Nad Trojou streets in Prague 8, rising from 212 to 260 metres. It protects Ordovician shale outcrops of the Šárka Formation and the dry grasslands and shrubs above them, split into two parts.

The slope was wooded with sessile oak until early farmers cleared it for pasture; Müller's 1720 map records vines here, and the Josephine surveys of 1836–1852 show grazing and later orchards. It was declared a natural monument on 1 September 1982 under code 760, then re-declared by decree 17/2002 effective 1 November 2002.

The name Trojská comes from the Troja district; the slope lies between Trojská and Nad Trojou streets. Once a year, at the turn of June and July, one half to two thirds of the area is mown and the cut grass is left standing over winter. In June the rare Rosa gallica flowers here with purple blooms.

The monument lies on a steep southeast-facing slope between Trojská and Nad Trojou streets, dropping from 260 m to 212 m above the Vltava. The most valuable eastern part is fenced off because visitors wore paths into it, so stay on the open ground. Mowing of one half to two thirds of the site takes place once a year around late June and early July.

The eastern part, the most valuable section, had to be fenced off because visitors wore footpaths into the slope. Some steppe wasps and true bugs living here occur nowhere else in Bohemia; the nearest sites with the same species are in southern Slovakia and Hungary.