The cascade was originally built in the 70-80s, during the soviet era. It was renovated and opened again in 2009. It's a wonderful place of nighlife, art and culture, and generally a big focal point for the young people.
The cache is a black MAGNETIC Nano, hidden as its name implies at the edge of the cascade. But the edge in this case is double sided, as it is a balcony type area covering the final steps.
This cache is the second in a series of 4, that will end with your victory in reaching the victory park and witnessing the awesome mother armenia statue and the great view from the top.
The cascade ends on the city centre's side at a lower point from where this cache is. This cache's location and that edge are connected by metal staircases and a little strip of asphalt. This cache is on northern side of the cascade.
Remember to bring your own pen, and look out for other caches in the bottom cascade area.
At this location also enjoy the huge obelisk-like monument. I am not sure what it was erected for, but it was impressive: standing so tall and me, alone, staring it back...
Wikipedia link about the cascade: https://en.wikipedia.org/wiki/Yerevan_Cascade