At the same time, city-dwellers were eager to see skyscrapers tower over the horizon and airships dotting the skies. Then there was the problem (or perhaps prospect) of limited land space and the subsequent necessity of migrating off-planet. Could we build a metropolis on Mars? It shouldn't be impossible, we thought, given how we redesigned city streets to accommodate cars instead of carriages. And after cave cities and skyscraper landing fields, why not? People moved to cities in pursuit of a dream, and with that same spirit, urban planners envisioned novel solutions for the cities of tomorrow.