[cesarb]

> There are very few places in the world with two large lakes, separated by a lot of height and not much distance.

You only need one large lake (or a place which can be dammed to create one); the other one can be completely artificial, with no water inflow or outflow other than through the pumps/turbines. In fact, I think it might even be possible to make both reservoirs completely artificial, and fill them by pumping water from somewhere else. That makes the necessary geography a lot less rare; you only need the appropriate height difference, and the ability to create artificial reservoirs on both ends.

[londons_explore]

Yes, but large artificial lakes aren't known for being cheap.

Pumped storage needs big lakes - a swimming pool on the top of a mountain isn't going to cut it.