https://www.visitcruachan.co.uk/
It isn't practical to build mountains, so you need to find some natural mountains you don't mind cutting a big hole into, with a pre-existing lake at the top, at the bottom, or ideally both, and then spend a lot of money building the storage system, plus hook it up to the grid.
The US does have lots of spare mountains, but they aren't exactly in the middle of cities where it would be convenient, so the infrastructure cost is very large.
In the UK one rationale for these sites is that they have Black Start capability. In the event of a complete network failure, there is no grid power, most power stations can't be started from this situation, they need the grid first. At suitably equipped pumped storage sites a relatively modest amount of local electrical power (e.g. from a portable diesel generator) is enough to get the site running with no outside help, whereupon it can produce, for a few hours, a great deal of electrical power for the grid, and other generators on the grid can use that power to start themselves up safely. By the time the reservoir is empty, lots of other generators are back online. Black Start justified paying them money to exist even back when they weren't regularly used. Today cheap wind power means pumped storage is economic anyway, fill it up at night with cheap power (sometimes at negative cost) and then generate electricity in the early evening peak with all that water.