If you haven't had the pleasure, you should secure yourself a copy of Italo Calvino's invisible Cities. Here's a brief excerpt about the city of Octavia, the spider-web city:
"Now I will tell you how Octavia, the spider-web city, is made. There is a precipice between two steep mountains: the city is over the void, bound to the two crests with ropes and chains and catwalks. You walk on the little wooden ties, careful not to set your foot in the open spaces, or you cling to the hempen strands. Below there is nothing for hundreds and hundreds of feet: a few clouds glide past; farther down you can glimpse the chasm's bed.
This is the foundation of the city: a net which serves as passage and as support. All the rest, instead of rising up, is hung below: rope ladders, hammocks, houses made like sacks, clothes hangers, terraces like gondolas, skins of water, gas jets, spits, baskets on strings, dumb-waiters, showers, trapezes and rings for children's games, cable cars, chandeliers, pots with trailing plants.
Suspended over the abyss, the life of Octavia's inhabitants is less uncertain than in other cities. They know the net will only last so long.”
Could anyone construct such a city? Perhaps the Hammock Caravan?