The highest point of Sintra Mountain is Cruz Alta, 528m above sea level.  The geology of the mountain is mainly a magmatic massif that has occurred through tertiary limestone plateaux. It is interpreted as a “ring structure” (similar to those of Scotland or Western Africa) with a high range of petrographic variety. In the summer months, due to a microclimate, the top of the mountain is sometimes covered by a characteristic mist that gives it the appearance of cloudy, tropical forest. This is the reason that Sintra mountain is green year around. 

The forest as we know it now, was planted in the 19th century and beginning of the 20th century with romantic influence, by King Don Fernando ll, William Beckford and Francis Cook. The 200 hectar Pena Park alone hosts over 500 species of trees and over 2000 plant species in total, hence the reason that a lot of Sintra seems to be straight from a fairy tale.  

Large parts of the parks and gardens were provided with water, partly to create hydrological conditions for acclimatization of wet sub-tropical or tropical plants, and above all to provide movement and sound effects in the three-dimensional stage-set which was a Romantic garden: hence the laying and making of kilometres of buried pipes and drains along the sides of paths and walks, and the creation of gushing woodland brooks, all leading to cascades, canals, ponds, and lakes.  All of this makes, in addition to a beautiful landscape, a wonderful scenery for walking and hiking in the area.