My condominium rental on Primero de Mayo is 20 meters from the Yanuncay River. 3 or 4 times a week mostly during the afternoon a herd of 6 Holstein cows graze across the river. Each cow is chained to a spike allowing them about 5- 7 meters of grazing area. The smallest calf I've nicknamed "Violetta".
You can see them graze in this short Youtube video below. The cows seem to be unaware of the river or the traffic noise.