Also referred to as Stag Moat, this moat originally served as a part of Prague Castle's fortification. The name comes from the fact that the area was used for deer breeding and hunting, during the reign of Rudolf II. Though you won't probably spot deer here nowadays, the moat is accessible in summer months and it is a popular strolling spot.
Wikipedia https://en.wikipedia.org/wiki/Deer_Moat
Official Website https://www.hrad.cz/en/prague-castle-for-visitors/gardens/stag-moat-10260
Address 39/6 Vikářská, Praha 11900, Czech Republic
Coordinates 50°5'29.791" N 14°23'58.946" E