On this day many Christians celebrate what is called in Greek Ὕψωσις τοῦ Τιμίου Σταυροῦ (literally, "Raising Aloft of the Precious Cross"). I've also heard it called The Exaltation of the Life-Giving Cross. It is all too much for me, as a Jew, to understand.
But I must admit I was surprised and pleased to see this first cross pictured below as a tree of life, blossoming and rooted in the earth! Life-giving.
In Judaism, the Torah is our tree of life. In the synagogue service we hold the Torah scroll and sing "Ets chaim hee..., It is a tree of life to those that hold fast to her."
Khachkars, or cross-stones, have been made in Armenia for over a thousand years. The cross-tree khachkar is a model of the of the Armenians' concept of the world during the Middle Ages.
The idea is explained well at the Khachkar website.
The khachkars above are in the wall outside St. James church in the Armenian Quarter of the Old City of Jerusalem.
This cross-stone is in the courtyard of the Armenian Catholic church on the other side of the Old City. It recalls the Armenian genocide, a painful and complex chapter of history still waiting for recognition.
UPDATE Aug. 2016: More about khachkars and other things Armenian here:
UPDATE June 2017: About a medieval cemetery in Armenia: https://www.thevintagenews.com/2017/06/21/armenian-cemetery-has-worlds-largest-collection-of-khachkars-stone-crosses-that-protect-the-soul/