Běh Advenťáka - Praha is a 6.45 km road race in Prague. The event is also called “Pětka,” Czech for a five-kilometre-style race, though the route is slightly longer than a standard 5K.
The listing is brief, directing runners to the official behadventaka.cz page and noting 256 participants in a past edition. Appearing in a Czech public race calendar, it seems to be a local mass-participation run, not exclusively for elite athletes.