I kept spending two hours at the gate in an airport in cities that I've never seen - London, Zurich, Madrid.

So I built Layfare (https://layfare.com). Give it the trip you're planning, and it shows you every city you could stop in for one or more nights, and what it costs compared to flying straight through. Often there's a minimal cost increase, or even a cost savings. If I'm flying to Dubrovnik from Philadelphia in late February, I can actually save over $200 if I stop for a couple of nights in Zurich.