The holy grail, symbol of the union of male and female.
One of my favorite temples is the one in Java, Candi Sukuh. This because of the Mayan style pyramid and also because of the visual representation of yoni and lingam. Something that is more stylized in Indian temples.
Mostly they are called Shiva lingams, even if the yoni part clearly sits under it. The universe, creation and nature in general is the union of male female forces for creation. That is ‘god’. Not a male figure only. To understand that concept is the basis of most religions that became patriarchal over time.
Durga is equally important as Shiva. I believe, as my own research, this image might be the concept for the Christian holy grail, a union of male and female organ, together making a cup a symbol in antiquity used for creation. The cross, being the ever revolving skies. In any case, you will never look at the cup of the priest the same.
Edit: 5-3-2019 Wayne Hershell made me aware of research he did in 2005.
I have not seen his research but he came to the exact same conclusion. He links it to the stars, yet I find it more a symbol of male female union as seen in Hindu temples. However, since he published this link between the grail and the candi sukuh image before, all credit goes to him for that, even though we came to this conclusion independantly and my research differs from his.
Here is a link to his article: http://thehiddenrecords.com/trinity?fbclid=IwAR3u-Nf0We0nuanKGbgfghGwr_MAIIupB6zYqswTTiUxk5TI_JK6of51ZRU