Friendship Temple (Freundschaftstempel)

In the middle of the forest stands this temple. It is worth leaving the castle garden and hiking past the obelisk to this small temple.

The catacomb, memorial for dear dead, is hidden in the Boberow Forest, to the right of the Malesherbes Column, near the Böbereckensee.
In 1992 the monument was restored.
This "temple" is built of field stones and looks quite simple.
Prince Heinrich had it built as a symbolic grave monument in 1790.
The inscription he wrote on the portal in French explains the symbolic value of this memorial site:
O you whose ashes are mingled, beloved relatives, steadfast friends, faithful servants, it is to your memory that I dedicate this monument.
Death respects neither rank nor sex nor age, and he who has survived so many losses has nothing but the sweet comfort of memory.
Walker!
Whoever you are, shed some tears at this grave!
Is there a heart that does not mourn for a thing dear to it, or thinks that one day the somber woe will come to cover it with its veil of mourning?
Small metal plaque with reference to the former friendship temple.
On the right behind the memorial for dearly departed one discovers a small metal plaque attached to a rock, which marks the place where a so-called octagonal "Temple of Friendship" - also known as the Jupiter Temple - stood at that time.
In this "temple of friendship", a small domed building, Prince Heinrich took care of himself
to dine when the weather permitted a trip across Grienerick Lake.

(Source: hobbyuo.de)

If most tourists ignore it, it is not in the travel guide.