A Mega-Block (also known as Housing Blocks or simply Blocks) are strato-scraper arcologies that are hundreds of stories tall.
Each building is a housing project tower that houses entire cities' worth of residents, some numbering in the hundreds of thousands. Blocks contain shopping malls, parks, food courts and other amenities the residents might need. They are connected to each other by zoomways (special high-speed highways).
Mega-City One was only designed to house 350 million residents. Judge Dredd says in a voiceover narration at the beginning that the population of the city is 800 million people. The population of Mega-City One soon swelled to an astounding 800 million people with crime rates skyrocketing so badly that people were afraid to leave their homes. The solution to this and the overcrowding was building up; "Mega-Blocks", gigantic housing project towers capable of housing entire cities' worth of populations from birth until death without anyone ever having to leave. Corruption and crime flourished in these environments, with many Judges refusing to enter. An average of 17,000 crimes are reported daily in Mega City One. Things are only made worse when an addictive new drug called "Slo-Mo" is introduced, which slows the user's perception of time to 1% of normal. The drug is a hit with junkies, who use it to make the bleak, horrific metropolis more beautiful. One Mega-Block, Peach Trees, becomes corrupt and rich when the drug's creator, a sociopathic, ruthless prostitute known as "Ma-Ma" uses it to front the drug operation.
Numerous Mega-Blocks are seen in the Dredd universe, the most notorious of which is Peach Trees.
As part of the defense scheme for Mega-City One that was chartered in 2052 each Block is meant to have its own Citi-Defense Militia. Sometimes rival gangs will fight for control of a Block in a Block War. Sometimes however some blocks had their Citi-Defense Militias destroyed by wars. Such as in the Peach Trees where even before The Great Block War of the 2090s the Peach Trees had already lost its Citi-Defense Militia and now had 3 rival gangs fighting for it.
In the Judge Dredd comics they are ironically named after actors, celebrities, and fictional characters, usually as a sly reference to the prog's plot. Judge Dredd lives in Rowdy Yates Block, which is named after Clint Eastwood's character in the TV series Rawhide.
In the 2012 film the name for Peach Trees Block was coined from the name of a restaurant in Shrewsbury, Shropshire County, England called The Peach Tree. It was the place where screenwriter Alex Garland and Judge Dredd creator John Wagner first met to discuss the film. This of course led to fans thinking Sector 13 was part of or near Atlanta,Georga, due to Atlanta being known as the Peach Tree City. The Peach Tree Block and Sector 13 are actually located in Trenton, New Jersey.