The earthquake of 1972 was so devastating, and the likelihood of future quakes so high, that Managua’s historic centre was basically abandoned. The entire city moved to the suburbs, clustering around the malls being built out there. The historic centre of Managua today is a mix of government buildings and melancholy ruins (the cathedral looks like a film set). The only people you will meet here are bored policemen and squatters. Nearby is Lake Managua, polluted beyond use.
Managua is also home to a number of crater lakes, other historic ruins (like the last vestiges of the palace of the Somoza family), countless monuments erected by the various generations of dictators and revolutionaries, and some debatably ancient human footprints.
The malls are where modern Managua goes about its business. They are the blandest part of the country, and yet also the areas in which you’ll have most difficulty finding a cheap plate of gallo pinto. Close to the malls, though, you can find Managua’s ethnic enclaves (try the Korean enclave right by Metrocentro if you want decent spicy food or a hot shower/sauna), its best nightlife, its universities and its most vibrant street art.
Realistically, though, no one comes to Nicaragua for Managua. It is swelteringly hot, the traffic is aggressive, the people are less friendly, and when it rains the streets turn to rivers of trash. Meet one of the resident expats in the city and they will ask you what the hell you’re doing in the city. Reply with ‘doing justice to Nicaragua’, and then think about moving on.