Situated in the East North East of Malta, this site is a Level 2 Area of Ecological Importance (AEI) and a Level 1 Site of scientific importance.
Biologically, Wied Għollieqa is important for a number of species that live in the area, such as the weasel (Mustela nivalis) which is very rare and reported to live in Wied Għollieqa. Other species include a number of fungi that are rare on a local scale or also on a European scale, such as Inonotus indicus which has been recorded for the first time in Europe from Wied Għollieqa itself. Following reforestation, Wied Għollieqa also houses the largest population in the Maltese Islands of the national tree, the sandarac gum tree (Tetraclinis articulata) giving the area a very high conservation value due to the rarity of the tree. The site is also important since a number of trees protected within the Trees Directive are present in the area and a number of protected birds also use the valley as nesting grounds.
After large amounts of rainfall, a freshwater stream flows down from San Ġwann and is stopped by a small dam beneath San Ġwann ta’ l-Għargħar. Any water not stopped by this dam, however, overflows into its original course and collects into a depression, enclosed on one side by another dam which allows the formation of a freshwater pool. The freshwater pool is however totally exposed to sunlight and air currents and thus water is quickly lost by evaporation and by seepage through the porous bedrock.
The dam maintaining the water in the freshwater pool was constructed in the 1970s mainly for the storage of water but also with the aim of preventing flooding in parts of Gżira. Along the years, however, this wall suffered damages, mainly due to underlying tree roots. For this reason, the Storm Water Unit of the Works and Services Division intervened and repaired the wall to its original state and also excavated part of the valley to rock level in order to hold water there for the ground to absorb. This repair was done between July and August of 2009.
Geology & Geomorphology
It is quite likely that Wied Għollieqa is a river valley and was formed due to erosion during the Quaternary pluvial period. Formation due to tectonics is unlikely due to the absence of main geological faults in the area.
The main rock outcrop is Lower Coralline Limestone but is only exposed in parts of the valley where garigue and steppe are evident.
Structures in Area
The north side is built up with numerous villas and a hotel (which also comprises two tennis courts which are built right in the centre of the valley) while to the south one may find the University of Malta, built in the 1960s (then called the Royal University of Malta). Other landuse structures present include the water catchment area and the adjacent dam, numerous rubble walls (ħitan tas-sejjieħ), the car park, the għorfa and a tree nursery which houses a number of saplings.
The environs of Wied Għollieqa are also home to a number of archaeological remains found in the area. Bugeja (2005), states that in the mid-20th Century, a site was documented to have been found, (though it has not survived) together with flint and prehistoric sherds.
Other remains found in or near Wied Għollieqa include pottery vessels from the first phase of the Bronze Age, a tomb dated to after 50AD containing cremation urns, pottery flasks, jars, saucers, lamps, two female skeletons and one male skeleton, a tower and a cistern (at Ta’ Cieda) and cart ruts (at Mensija).