The halachic concept of kedushas makom - geographic sanctity - is introduced in Parshas Terumah. The Mishkan, and later the Beis Hamikdash, was endowed with holiness. Chazal (Keilim 1:6-9) delineate distinctions within the geographical sanctity that permeated the Beis Hamikdash: The Kodesh Hakodoshim (Holy of Holies) was endowed with a greater degree of sanctity than the Heichal (Sanctuary), which in turn was holier than the courtyard. There were ten distinct levels of geographic holiness, the lowest level being Eretz Yisroel at large. Outside Eretz Yisroel, no geographic sanctity exists whatsoever.
In delineating the gradations of holiness the mishna emphasizes that there were practical differences that resulted from these distinctions. The Kodesh Hakodoshim was distinct in that no one except the kohein gadol on Yom Kippur could enter, in contrast to the Heichal where other kohanim could enter on a daily basis. The practical ramifications of levels of sanctity, are also seen in the realm of time. Shabbos is holier than Yom Tov and this is reflected by practical differences such as the permissibility of certain activities on Yom Tov that are prohibited on Shabbos.
The mishna highlights the halachic distinction between Eretz Yisroel and the rest of the world. The korbanos of the omer and the shtei halechem of Shavuos can only be brought from grain that grew in Eretz Yisroel. Although this distinction is halachically accurate, it seems strange that Chazal singled it out- there are many other differences between Eretz Yisroel and chutz la'aretz such as the agricultural mitzvos of Terumah and shemittah. Why highlight the omer and shtei halechem?
The sanctity of Eretz Yisroel is two-fold. Eretz Yisroel is endowed with kedushas karka - holiness which emanates from the ground and expresses itself through the mitzvos hateluyos ba'aretz - the agricultural mitzvos, but there is a second dimension of kedushas Eretz Yisroel. The Beis Hamikdash is holy because it houses the Divine presence though the kedushah has gradations. The closer to the center of the mikdash - the Kodesh Hakodoshim - the greater the degree of holiness. At what point does kedushas hamikdash end? The absolute outermost boundaries of the Beis Hamikdash are the borders of Eretz Yisroel.
The mishna that delineates the distinctions between Eretz Yisroel and chutz la'aretz is not focusing on the distinctions within agriculture. The ten distinctions of the mishna are the gradations within kedushas hamikdash. That Eretz Yisroel is part of the Beis Hamikdash is expressed in the requirement that the korban omer and shtei halechem be brought specifically from Eretz Yisroel.
Besides the halachos of agriculture and korbanos that differentiate Eretz Yisroel from chutz la'aretz, there are other distinctions as well. Semicha - the transmission of tradition handed from teacher to student dating back to Moshe - can only be conferred in Eretz Yisroel. Similarly, the declaration of Rosh Chodesh can only occur in Eretz Yisroel. These two halachos point to a third dimension of Eretz Yisroel's uniqueness, its primacy as the place of Torah study. Only there can the authentic chain of transmission be continued. The declaration of Rosh Chodesh, and the dependent determination of the yomim tovim can only be made by a beis din in Eretz Yisroel. Torah scholars of the highest level are given the authority to decide this matter which affects the entire Jewish people.
This third aspect of Eretz Yisroel, its place as the pinnacle of Talmud Torah, is closely linked to its unique role as being the outermost precinct of the Beis Hamikdash. The Ramban (Terumah) explains that a primary purpose of the mishkan was to enable the Har Sinai experience to remain alive for eternity. The luchos were at the center of the mishkan, and later the beis hamikdash. The mishkan, besides being a place for korbanos, was also the center of Torah. It is for this reason that the Sanhedrin sat in the Beis Hamikdash. If Eretz Yisroel is the outermost area of the Beis Hamikdash, it is also the outermost area blessed with this unique aspect of Torah. Har Sinai remains alive in the Beis Hamikdash and, by extension, throughout Eretz Yisroel. For the unique Torah experiences such as semicha and declaration of Rosh Chodesh, only a place which is a continuation of Har Sinai is acceptable. Eretz Yisroel, as the outermost precinct of the Beis Hamikdash, qualifies for these mitzvos as it does for the korbanos of the omer and shtei halechem.
Following the descriptions of ma'amad Har Sinai in Parshas Yisro and Mishpatim, we are given Parshas Terumah to keep the experiences alive. To visit the Beis Hamikdash is to revisit Har Sinai. To learn Torah in Eretz Yisroel is to enter the mikdash and reconnect to Har Sinai.