Lisbon is a very hilly city.
The public transportation system in Lisbon is a quaint mix of old and new. There's a tram system over a hundred years old; on it run both historic trains as well as sleek modern ones. There's also a modern bus system and a subway. And all of these systems run north, south, east, and west all over town.
But it's the only city I've experienced in which the public transportation includes elevators which take you up and down.
The most famous of the three vertical forms of public transit is Santa Justa's Elevator which takes you from just off Rossio Square downtown six stories up a steep cliff face to Carmo Square in the Barrio Alto district. Without it, you'd have to go the long way around.
There is a Baixa-Chiado Metro stop on the uphill side of the elevator, and if your spatial relations are still intact, this tells you that the metro runs six stories below the surface. Coming out of Baixa-Chiado station requires four consecutive long escalator rides. Of course, people in Moscow read this and scoff, "You call that a long escalator ride? This is a long escalator ride."