The Sunken Garden’s official name is Gen. Antonio Luna Parade Grounds. The UP ROTC took care of it way back when the campus was installed in Diliman in 1949. The field has then been used for training, parades and clubs like football and Frisbee use it regularly, too. Of course as so many will know today, it is also the venue of many other activities like concerts and the U.P Annual Fair.
(Wikipedia) The Gen. Antonio Luna Parade Grounds is a 5-hectare natural depression found on the eastern side of the campus and at the end of the Academic Oval circle. Sunken Garden is enclosed by the U.P. Diliman Main Library (also houses the School of Library and Information Studies), College of Social Sciences and Philosophy’s Department of Psychology, College of Education, Student Activity Center/Vinzons Hall, College of Business Administration, School of Economics and College of Law. The Grounds was the original property of the UP-ROTC when the campus was founded in 1949.
Gen. Antonio Luna Parade Grounds acquired its name Sunken Garden due to its basin-shaped low-level formation that has the deepest point of 65 meters above sea level (contrary to university’s height of over hundreds of meters above sea level).The Sunken Garden is the venue annual U.P. Fair as well as for sports tournaments, including football, frisbee and volleyball. Sometimes, the Department of Military Science and Tactics hold training in the area. One of the more popular activities held in the Sunken Garden, is the Latagaw Cup, a competition organized by the U.P. Latagaw Brotherhood, a university-based fraternity.
The Sunken Garden actually sinks by about two inches every year. There are two possible reasons of this sinking: first, it is because of underground trenches that mingle with the campus’ sewer system. These trenches branch from the rear side of NIGS building, Sampaguita Residence Hall, the U.P. Integrated School, down to the National Institute of Physics, until near the former Narra Residence Hall. These trenches then connects to the Marikina Fault Line, an active geologic structure that runs across the east of Metro Manila. Another theory is that the depression was due to the emptying of former streams in the Sunken Garden that were prominent in the 1950s. These streams formerly run from the Katipunan Avenue, going to the garden itself and leaves the campus for the Commonwealth Avenue.