Abstract
According to historical and archaeological sources, the ancient city of Esfarayen was one of the important settlement centers of the Islamic era. During its existence and prosperity, this city was a link between the two famous and big cities of Nishapur and Jurjan, but from the end of the Safavid period onwards, due to various reasons, it declined and its inhabitants gradually moved to the new city. So far, parts of the ancient city of Esfarayen have been excavated by archaeologists during several different seasons. In the meantime, choosing a suitable place for archaeological excavations in this area has always been one of the most important issues for its explorers, because due to the limitation of financial resources and the large area of the area, it was necessary to determine suitable places for excavation in advance. so that its archaeological exploration can be done with more certainty. For this purpose, at the beginning of the third season of excavations, six hectares of the city were investigated with the help of magnetometric method. Then, based on the results of magnetometry, the excavations of this season were carried out. According to these explanations, the main goal of the current research is to present the results of magnetometry and compare it with the findings of the archaeological exploration of the ancient city of Esfarayen. In the current research, the descriptive-analytical method has been used using the results of field and library studies. As a result of these studies, many evidences of industrial activities were identified in the site, including architectural remains of a pottery kiln and many evidences of pottery production, which are important in the archaeological studies of the Islamic era.
Keywords: Magnetometry, The Ancient city of Esfarayen (Balqis), Esfarayen.

Introduction
The ancient city of Esfarayen, which today is known as the city of Belqis, is located in a vast plain, three kilometers southwest of Esfarayen, with an area of nearly 200 hectares. Currently, this city consists of different parts such as Arg, Sharistan, Rabz, Hesar and Khandaq. According to the documents obtained in the archaeological excavations, the city of Balqis had a settlement from the first centuries of the Islamic era to the beginning of the Qajar period (Vahdati and Nik-Govtar, 2016: 98). Due to the importance of this city in the past, several seasons of archaeological excavations have been carried out in it (Vahdati, 2016, Vahdati and Nik-Govtar, 2018 A and B, Farjami and Sotoudeh, 2019). But Balqis has a large area and the excavations that have been carried out so far do not even cover a small part of the city. For this reason, it was necessary to use remote sensing methods to identify at least a significant part of the city’s landscape and buried bodies. One of these methods, which is considered one of the branches of geophysics, is magnetometry. According to these cases, in 2009, and with the aim of identifying part of the layers buried under the soil and choosing better places for exploration, first a part of the area was surveyed for magnetometry (Aminpour, 2010). In this investigation, about six hectares of the area in a place called Tepe-Minar and also the northern part around the citadel in the southwest side of the city were surveyed by geomagnetism. By carrying out this investigation, results were obtained, based on which the third season of archaeological excavations of the site was carried out. According to the aforementioned, the main purpose of the current research is to investigate and analyze the results of the magnetometric survey of the area and the exploration that was carried out based on it. The most important question that we are trying to answer in this research is to determine the effect of the magnetometric method on choosing a better place for the purposeful exploration of the Balqis area. The method and approach of the current research is descriptive-analytical, and the method of gathering information is based on field studies from magnetometry and archeological excavations of the site, as well as library studies.

Discussion
A- The area known as Tepe Manar The results of magnetometry survey: This section included 36 grids of 10 x 10 meters. In some parts of this section, confused and jumbled magnetic anomalies were recorded, which probably indicate the transformation and destruction of its subsurface artifacts. But in other parts, the magnetic gradient anomaly map showed evidence of architectural structures and other buried ancient phenomena. Accordingly, in the part marked with the letter F, anomalies were revealed that could be related to heated masses such as brick structures or terracotta masses. The results of archaeological excavations: In order to measure the investigated parts of Tepe Manar with magnetometric method, three test boreholes were dug in the discussed area. In the first borehole, all the piles of clay and ash were encountered. In the second borehole, layers were identified, the surface and subsurface layers are sand, sand and soil, respectively, and there is a mixture of ash and soil in the lower layers. Inside the texture of soil and ash, a large amount of welding furnace and pottery was obtained. Borehole No. 3 also did not find any architectural works and only a pile of clay and ash was identified in a hole. B- The north-eastern area of the citadel the results of the magnetometric survey: In the magnetometric survey of this part of the city, several anomalies were identified. In this range, anomalies have been revealed in the form of light-colored extensions and in some cases perpendicular to each other, which can be related to the buried clay architectural structure. The results of archaeological excavations: In the scope of the second part of the geophysical survey, three boreholes and trenches were opened and explored. Borehole number one hit a pile of glazed pottery from the 6th century AH. It seemed that there was a pottery workshop around this place, because most of these pots were covered by the wastes from the pottery activity. For this purpose, a trench was excavated near borehole 1, measuring 6 x 6 meters. After removing the surface layer, a pile of pottery shards and pottery kiln debris was encountered, which were scattered on the surface of the trench at different depths. For this purpose, another borehole with dimensions of 2 x 2 meters was created at a distance in the southern part of trench 2, and after removing the surface layers at a depth of 30 cm, the remains of a pottery kiln were identified. The reason for the large amount of strong magnetic anomalies in this area is the presence of many pottery pits in this area, in addition to the pottery kiln. The date that can be determined based on the pottery obtained from this kiln is the second half of the 12th century A.D.

Conclusion
Today, in the world, magnetometry is widely used by archaeologists to identify architectural structures and buried structures. By using these methods, it is possible to examine and study many parts of an ancient site without destruction in a limited time. For this reason, in the archeology project of the old city of Esfarayen, the magnetometric method was also used during a period. Because not only the area was large, but also the limitation of resources prevented it from being able to explore a large part of it. About six hectares of the area were studied in the magnetometric survey of the area, which was carried out with the Fluxgate device. After investigating and preparing the related map, anomalies were observed in some parts of the map, which were probably related to industrial activities. Based on these anomalies, six boreholes and trenches were dug in two parts of the area to measure the results of the magnetometric survey. In almost all boreholes and trenches obtained from the excavation, evidences of industrial activities such as pottery production or pits of potter’s pits were identified. The existence of these convincing evidences is a clear proof of the magnetometric anomalies of the area. In a trench, very clear evidence of an Islamic era pottery kiln was found, around which there were several waste places. Considering these cases, it can be said that the results of the archaeological excavations of this site are a confirmation of its magnetometry project. If these studies continue and boreholes or trenches are created in other parts, we can gain more knowledge about the different spaces of the ancient city of Esfarayen.