The most obvious question is: what does it mean? Well, the online Encyclopædia Britannica defines stela as: standing stone slab used in the ancient world primarily as a grave marker but also for dedication, commemoration, and demarcationand the plural of stela is stelae (so the word is mispelt on the sign, though I guess not too many people notice that).
According to Lonely Planet, there are 82 stelae still present in the temple of Literature, and they were made in celebration whenever someone passed the highest exam (and so became a 'doctor'). A picture of one of them is on the right.Though visitors seem to be quite obedient in not writing, drawing, stepping or sitting on the stelae, that doesn't stop them stroking the head of the turtle at the base ‒ local people seem to believe that stroking the head of a turtle, even a stone one, gives you good luck.
Anyway, one more thing we might note: as there were lots of doctors, the possessive of doctors should be doctors', with the apostrophe after the 's', not before it. It is interesting to note that users of English in Vietnam have problems with apostrophes, just like people in Brunei. (See my blog of 8 February on the issue.)
