Sector 7 is one of the eight sectors of Midgar and one of the six sectors that you are able to visit. Check out the full Midgar location page for more information on the different sectors.
Sector 7 is where Tifa’s Seventh Heaven, the pub and local hideout of team AVALANCHE, is located, along with some other houses and shops.
The story of the game takes you through Sector 7 in the very early stages of the game. You cannot revisit Sector 7 though later on in the game as it is destroyed when Shinra blows up the pillar that holds the upper plate perched precariously over the slums.
There isn’t anything important that you can miss in this area though. Have a look at the first page of the walkthrough for the sections that include Sector 7.
You can purchase the following items in the shops:
The map below shows the location for Midgar on the World Map:
Potion
Fire Materia
Iron Bangle
Assault Gun