Question:

What is so special about the Holy Temple that is constantly mentioned in our prayers?  It's just a building!

Answer:

The Jewish people have been mourning the loss of our Holy Temple in Jerusalem for over 2,000 years.  We daily beseech G-d in our prayers to rebuild the Holy Temple, speedily in our days. What is this whole fuss over a destroyed sanctuary? 

The Holy Temple is a lot more than a synagogue.  In truth, every synagogue and in fact, every Jewish home, is a miniature Holy Temple which is consecrated and sanctified to G-d. However, the Holy Temple is exceptional because holiness was manifest there more than in any other place on earth.  The Temple was built on the Temple Mount in Jerusalem, in the exact location that G-d had chosen as the holiest spot on earth.

Although the Holy Temple is a physical edifice of wood and stone, it corresponds to a more spiritual domain.  Our sages taught that "the Holy Temple below is positioned opposite the Holy Temple on high."

Each detail of the Holy Temple corresponded to a spiritual counterpart in Heaven.  In the First and Second Holy Temples, this correspondence was not seen in every detail, while in the Third Temple, we will be able to clearly sense the spiritual significance of every detail of the building. 

Thus, the Holy Temple is the only spot on earth where G-d's presence can be palpably felt.  We can get a little foretaste of the special quality of the Holy Temple every time we pray in the synagogue or perform mitzvot at home.  Whenever we do so, we are elevating a physical place and making it a home for G-d.   In fact, all synagogues and Jewish homes in the world will attach themselves to the Third Temple building, may it speedily be rebuilt. 

(From Exile to Redemption, p. 59.  Midrash Tanchuma, Parshat Mishpatim, 18.  Likutei Sichos vol. XXIX, p. 22)