We'll always have the Moon.
No one will mourn those cities; but shamefully the village-scale ancient culture that had survived the Cultural Revolution because it was 'far from the flagpole' was lost.
Here's low-cost scalable energy storage to compete with gravity-electric systems:
Firebricks offer low-cost storage for carbon-free energy | MIT News
It stores 'excess' energy as heat in firebrick. Which can be used directly as industrial heat or to drive turbines.