Honestly, if you build transit, developers will build.

I wouldn't call it "building a city", but if you look at Northern Virginia today, you'll find that vertical districts are popping up along the Silver Line metro that now extends past Dulles airport.

At the end of the metro, there is literally a "town center" residential area on one side with buildings around 5 stories tall. On the other side of the tracks is literally fields, but the roads have been laid out like Sim City with empty plots and developers are now beginning to construct buildings starting from the outside perimeter first, working their way toward the metro station.

Throughout the DC suburbs, you will find densely populated areas with relatively tall vertical buildings (15-20 stories) that simply were not there 20 years ago. Reston is a good example. I've watched 4-6 buildings (over 10 stories) get built in Reston alone. They mostly started when the the metro line was finished.

tysons is a good example as well. I always think the development of the DC metro is some of the most impressive in the sense of 'cities' popping up along the train lines.

I haven't travelled the entire country but I've never seen anything quite like Silver Spring, Bethesda, or as you say, Reston. Super interesting.