In Jak II, Jak visits this location on multiple occasions. Earlier in the game he destroys several Metal Head Eggs which are compromising the mining operation, and later he destroys the Main Control Tower and a Krimzon Guard Tanker Ship in an effort by The Underground to choke the Baron's supply of Eco.
The Drill Platform is a large scale Haven City mining operation equipped with a massive drill which is excavating the mountains below for Eco. It is held up far above the ground by spider-like legs. The Drill Platform is presumably located in the mountains west of Haven City, in the Icelands. It is also a docking area for Haven's Tanker Ships, one of which was destroyed by Jak.
There were many defence turrets - Gun Pods - as Jak used multiple in his missions on several occasions. There was also a Titan Suit, which could have been used as a means of defending the location. Despite its fortification, Drill Platform fell under the control of the Metal Heads.
Concept art would suggest that in fact several other Drill Platforms exist in other locations.
The Drill Platform can be accessed by the Warp Gate in the Power Station unless Jak is being sent on a mission to the Strip Mine. After completing the game, the Power Station warp gate will always teleport Jak to the Drill Platform.