The Soré Pool at Imne-ti-Soré

Huunos is an ex-capital of the Confederacy.
"At the foot of the Soré Falls they had built a sink hole, a second waterfall a short swirl from the first, dropping underground to an aqueduct which channelled the river into vast artificial caverns beneath a green valley they called the Soré Falls park. The park rose steeply towards the city and ended in a wall. Flying over it, you would see a huge rectangular pool, one kilometre wide and ten kilometres long, bounded by wide marble and brick highways at the top of its containing walls. The nearest equivalent to such a structure could perhaps be found at Versailles on Old Earth, but the ponds and pools of France's most grandiose designs were mere puddles when compared to the Soré Pool. It was fed from the upwelling of that water held under the park, a giant artificial spring kept out of balance with the gravity that would otherwise have flooded the valley by specially designed valves and a series of high volume pumps, part of the power supply for which came from water mills at the underground falls with a much larger fraction being supplied by the wave and wind turbine network that provided the rest of the city with electricity. The system made an extravagant demand on energy resources but the lambda who had built it considered the ultimate effect worthwhile.
The languid surface was ornamented with a hundred fountains, three artificial islands and four bridges which crossed it from east to west. Water lilies were cultivated in raised bowls and pale lights spread silently over stretches of dark water."