Between 1997-2001 an artificial cave with three water-bearing arms was exca\vated in the southwestern part of the Lower City. It is about 160 meters long and parts of the corridor were cut from the rock in the third millennium BC. The calcium deposit (cinter) was dated by the Uran-Thorium method. Four vertical shafts connect to the surface. In Roman times the entrance to the cave was enlarged and terracotta pipes were used to channel water into fish tanks in front of the cave. In the Byzantine period (12-13th century) a stone-lined channel led water to a small garden.
The cave was interpreted as a “corridor/path under the earth”, the notice at the site indicates “and by this referred to as the god Kaskalkur”. From other sources I understood that meant is: such an underground cave was referred to as “Kas.Kalkur” (Kas: road or tunnel; Kur: underworld). And in a treaty with the Hittite king Muwatalli II the name Kaskalkur is used as that of a name of a god one swears by. This might imply that god was also a god at Troia.
I found “In 1997 final confirmation came after Starke’s location of Wilusa – from an archaeological discovery: in the western area of the Lower City at Troia a spring cave with three arms for conducting water into a subterranean reservoir was excavated which ran more than 100 metres down into the mountain. Radiometric studies conducted by the Heidelberg Akademie der Wissenschaften in 1999/2000 showed that this was a man-made facility for providing water which had been dug by the early 3rd millennium BC. This discovery shed new light on a particular item in the Alaksandu Treaty: in § 20 of that treaty, in which the chief gods of the two parties to the treaty are invoked as witnesses to the oaths and wreakers of revenge on potential infringers of the treaty, one of the divinities of the land of Wilusa is also invoked "the way into the underworld of the land of Wilusa" (KASKAL.KUR). There can be hardly any room for doubt that the subterranean spring venerated as a divinity means the spring uncovered by the Korfmann excavation.“ Source: Joachim Lataz: “Wilusa (Wilios / Troia). Centre of a Hittite Confederate in North-West Asia Minor.