Wied Ghollieqa is situated in the North-Eastern part of Malta separating four highly built-up areas: San Gwann and Kappara lying to the North of the valley, Msida to the East, San Gwann Industrial Estate to the West and the University of Malta and Mater Dei Hospital to the South.

The valley runs in an easterly direction: its source lies in the area of the San Gwann Industrial Estate at an elevation of 55m and the valley drains eastwards towards Lazaretto Creek in Gzira. Originally the valley used to drain into the sea however, most of the original valley system has been lost to urbanization in Gzira. The areas surrounding the present valley sides are built up and in some cases buildings are only 10-20m away from the valleybed. The valley is also traversed by Triq M.A. Vassalli (better known as Regional Road) which has split the valley into two separate areas.

The valley is mainly composed of Lower Globigerina Limestone, although the valley-bed lies very close to the top of the Lower Coralline Limestone. For this reason, the valley-bed is highly permeable and drainage is largely by infiltration rather than surface flow.

Although most of the valley sides are composed of agricultural land, typical of most valley systems, the area is still characterised by extensive maquis communities whereas the valley-bed provides an important watercourse habitat. One of the most important characteristics of this valley is its richness in fungi. About 30 species of macrofungi have been recorded and these were found mainly in the maquis communities located along the valley-bed.

Mepa scheduled Wied Ghollieqa as an Area of Ecological Importance and Site of Scientific Importance as per Government Notice No. 241/97 in the Government Gazette dated 7 April 1997. The rest of the valley system, along the area known as Ta' Gannus, was scheduled as a Level 4 Area of Ecological Importance (buffer zone) as per Government Notice No. 869/09, dated October 30, 2009.