A nonstandard or incorrect use of the noun 'der Tempel' (the temple) as an adjective. It does not exist in German as an independent adjective.
example
Manchmal findet man in Texten den Ausdruck „ein tempelartiges Gebäude“, aber nicht „ein tempeles Gebäude“.
Sometimes you find the expression 'ein tempelartiges Gebäude' (a temple-like building) in texts, but not 'ein tempeles Gebäude'.
Usage tips
Wrong part of speech
'Tempel' is always a noun in German: 'der Tempel' (the temple). It cannot be used as an adjective to describe another noun. A phrase like 'ein tempeles Gebäude' is incorrect.
EXAMPLE
In der Stadt gibt es einen alten buddhistischen Tempel.
There is an old Buddhist temple in the city.
Description with '-artig'
To express that something has the characteristics of a temple, the suffix '-artig' is often attached to the noun. This creates the correct adjective 'tempelartig' (temple-like).
EXAMPLE
Der Eingang des Museums war tempelartig gestaltet.
The entrance of the museum was designed to look temple-like.
Compound nouns
Another way to create a connection to a temple is to form a compound noun. In this case, 'Tempel-' appears as the defining element at the beginning, as in 'Tempelanlage' (temple complex) or 'Tempelbau' (temple construction / temple building).