Introduction
Archaeology as a scientific system is indeed indebted to geography for processing of models and comparative studies on reconstruction of paleo-environments and paleo-landscapes, as wall as the patterns of human settlement. It is obvious that different types of existing settlements on the earth are the results of consequential interaction between human behaviors and environmental situation. This communication is obviously clear, in particular, in the case of soil and sedimentary lands, which are very important elements for husbandry and food production. Human impressibility of environment has always been the main reason for spatial differences of settlement and population aggregate and has caused the formation of specific settlement pattern in the ancient times. The aim of this paper is focusing and analyzing the role of natural and geographical elements as well as the environmental in appearance the human settlements in different periods of Mazandaran provinces in Northern Iran. In this region the Alburz chain, such a high natural wall with approximately 70Km wideth, extends from West to East of Mazandaran until Gorgan valley. While the natural and geographical conditions of Mazandaran province prevent easily access to the mountainous area located in the south part of Caspian Sea, it is also causes many problems to investigate and explore the evidence of human remains at this region. The other reason for deficiency of information about the ancient settlement situation of Mazandaran province acts as a kind of limitation for archaeological research in the region. Thus, the initial action for the purpose of this research was archaeological study.
Materials and Methods
To conduct the research, the methodology applied for data gathering will pervasive surface survey. Accordingly, all archaeological and historical remains will be identified and then record in details. The collected data, including 2475 sites and monuments from Neolithic to late Islamic period, were reported in 21 volumes. Dating the sites have been carried out based on sample recognition and comparing studies of collected surface data. The material gathered were divided into four general groups: prehistoric period, Iron Age, historic period and Islamic are. According to current research, from the total 2475 sites, 123 of them belong to pre-history periods, 256 of them belong to Iron Age, and 648 of sites present the culture of the Achaemanid, Parthian and Sassanian era. Finally, 1986 sites and monuments have shown the traces of the Islamic period which some of them show only a particular time of Islamic era and mostly present the monuments and architecture of this period.

Results and Discussion
For achieving the considered goals, the authars have implemented and analyzed geographical information, using Arc GIS 9.2 software and then, for interpretation of data, SPSS 11.5 software was applied. By establishing a data bank for the study, which is in the form of geographical information system, they carried out an analysis on spatial distribution of the sites. Thus, they focused on natural factors such as height, climate, flowing waters, rivers, flora (forest and pasture), and rainfall to understand the role and efficacy of each factor in appearance of the sites. the study made it clear that the ancient settlement patterns of Mazandaran was highly affected by natural factors such as flora, water sources, rainfall, and climate.

Conclusion
In addition, according to this research it has been specified that each natural factors have played different roles in distribution of the ancient sites and there is no the same precept for all. Thus, it is necessary that the role of each natural factor to be studied separately. Among the natural factors studied in this research, there are a positive and meaningful connection between distribution of the sites and the area of the raining layers, distance to the river, flora (forest and pasture). However, there is no significant relationship between the area of the layers of the height and climate, and the distribution of ancient sites.