Thirty-six hours is not enough time in Lisbon, but it is enough time to build a compelling case for coming back. I landed on a layover that was technically supposed to be spent in the airport lounge and instead spent entirely on foot.
The trams rattle up hills steep enough to question the engineering, and every other street corner has a viewpoint with a name and a small crowd of people drinking the local cherry liqueur out of chocolate cups, which is a genuinely good system that more cities should adopt.
I ate a pastel de nata standing up at a counter that has apparently been making them the same way since before my grandparents were born, and I am prepared to argue in any court that it was worth rearranging my entire itinerary for.
If you only have a layover, pick one neighborhood and walk it slowly rather than trying to see all seven hills. Lisbon rewards wandering more than it rewards a checklist.