Admittedly Lerna isn't much to look at. What is impressive is how old it is. Much of what you see is from the early Helladic era of 2500 -2000 BCE. In other words, earlier than Mycenea.
The site is reached by a brief walk from the highway south and west of Nafplion.
This may help to make sense of what you see.
Outside the shelter are other ancient walls and works.
As I say, not much to see. But search on "Lerna" to learn more.