The Shinra Underground Test Site is a location in Final Fantasy VII Remake. Located directly beneath Sector 7 of Midgar, it is a Shinra Electric Power Company laboratory that houses several specimens from Type-B to Type-E, used in experiments by Professor Hojo, and is part of the top secret Deepground network of research facilities.
Though its existence had been speculated by residents of the Sector 7 undercity, Cloud Strife, Tifa Lockhart, and Barret Wallace stumbled across it through a cave-in at the Sector 7 undercity residential area caused by the plate collapse.
The Shinra Underground Test Site was created at some point prior to the events of Final Fantasy VII Remake. Many of the specimens managed to escape, including the Wrath Hound, spotted by Wymer and fought by Cloud in "On the Prowl" during "Home Sweet Slum". Wymer later told Cloud of rumors of the test site's existence, which were as yet unsubstantiated.
After Shinra dropped the Sector 7 plate in "Fight for Survival", Cloud, Tifa, and Barret escaped in the nick of time. During "A Broken World", they returned to the site of the disaster to look for survivors. As they were led to Wedge by one of his cats, the now-unstable ground caved in and they fell into the test site below, and were separated.
Barret cleared the area alone, looking for Wedge as well as the others. He reunited with Tifa, but when they found Wedge, they were attacked by the released Shinra specimens. The two destroyed them, aided by Cloud who joined in the last moment of the battle, and together they readied to take Wedge and his cat back aboveground. The sight of the testing site with its tubes and humanoid creatures kept inside sparked some memories in Cloud. Cloud briefly recalled having spent time in a similar tube, but before he could think any further the Whispers ejected all of them from the site.
The Shinra Underground Test Site is located directly beneath the Sector 7 undercity's residential area. Following events of "Fight for Survival", a cave-in near Wedge's house leads directly to its top floor. The site seems to be entirely abandoned, with several escaped monsters that are barely contained, and apparently incomplete expansion projects.
The Shinra Underground Test Site primarily consists of large, dimly lit, concrete chambers that house specimens, from Type-B to Type-E, in cages. The bars of the cages are in many cases bent out of shape by the specimens within, which have escaped from them. Among the chambers are metal walkways and ladders to move between the test site's floors, and large metal doors in-between chambers. Inactive cranes are also seen partway-through abandoned expansion projects.
The test site is spread across six floors underground. On its bottom and second floor are nurseries holding the specimens in cages, where the bottom floor holds Type-C specimens, and the second floor is divided in two halves where one holds Type-D specimens and the other holds Type-F. The remaining lower floors comprise artificial tunnels, while the top floor houses a vast metal testing room, as well as several tubes containing human test subjects.
The artificial tunnels connecting the chambers of the Shinra Underground Test Site are held up by metal supports through the rocks underground. Wires run through the tunnels, and Shinra boxes are stashed on shelves running alongside them. Within these tunnels dwell monsters, including monsters that are seen above ground, such as the wererats and gorgers seen in the Sector 7 undercity's Scrap Boulevard.
Aside from the space used to house its specimens, a break room is located on the top floor, and a waste processing chamber at the bottom. The waste process chamber contains abandoned construction materials, presumably used to dig further underground and expand the site.
The Underground Test Site is first visited during "In Solitude" in chapter 13, "A Broken World". It is explored primarily by Barret Wallace, though Tifa Lockhart joins the party soon thereafter. The two fight several monsters before eventually fighting the Failed Experiment. Later, the map can be revisited in chapter 14, "In Search of Hope", with Cloud Strife leading the party, for sidequests.