Systems in place by daughterofshadows  

Chapter 1

With his hands bound, they led him through up the road and into the city, and though most of his attention was dedicated to not stumbling over his own feet, Tuor could not help but marvel at the intricate irrigation system woven throughout the city.
He had not previously considered how a city as large as Gondolin might manage to sustain itself, but the answer apparently was to use every available surface in the city for planting.
Did all elven cities employ such measures? It seemed difficult to imagine that the caverns of Menegroth could have such gardens, when so much of the city lay underground, but then again, who knew what was possible with a touch of magic?

"It is quite impressive, is it not?" said his captor, who had noticed his gaze.
"Ingenious, really," Tuor replied, "It must be difficult to ensure that the roof does not collapse under the additional weight."
"Ensuring proper drainage from the gardens was the greater challenge by far, but once you have made it work the first time, it becomes easier to do again. Even if it took many, many tries before Ídhrŷn was satisfied with the pipes we made for it."

Another elf walked out of an alleyway. "Barhador, I could not help but overhear you talking about my masterpiece." She looked at Tuor's captor with a teasing glint in her eye. "I trust you have only good things to say about it to our guest."