Porosity is one of the most important physical properties of rocks. Strength and deformation parameters as well as the effect and degree of weathering are also related to porosity. Rocks with high porosity are more vulnerable to weathering than are non-porous rocks. Consequently, identification of pore size and shape may assist the evaluation of strength characteristics and resistance to weathering. One approach used for the determination of macro pore geometry is the stereology method. The main principle of the stereology method is based on the analysis of three-dimensional solid materials on a two-dimensional surface. The macro pore geometry of rocks can be evaluated by the shape parameter ( F) concept, which depends upon the stereology method. Shape parameter is an explanation of pore geometry on a rock surface using the perimeter and area of the pores. Here, the shape parameter approach is utilized for the determination of the macro pore geometry in travertines. Studies were performed on yellow travertine cut slabs at the memorial mausoleum (Anitkabir) of the great Turkish leader Ataturk in Ankara, Turkey, and on fresh surfaces of the same rock in the quarries from which the slabs originated. Pore perimeter and pore area were calculated using Geographical Information System software. These shape parameters of the macro pores on travertine pillars and on fresh travertine cuts were then compared. As a result, a slight pore geometry difference between air-exposed and fresh yellow travertine was determined based on the statistical evaluations.