There is a real world city that sank into a limestone cave like Ancient Trokair.
It is called Ubar and it was a city in the Middle East that existed for 5000 years before finally being swallowed whole in 500 or 600 AD. The city prospered as a trade destination (particularly for frankincense, apparently) and its main advantage was the existence of an oasis. Over the centuries, the inhabitants drew up fresh water from a limestone cavern beneath the city. Once it was depleted enough, the cave roof collapsed and the city fell into the earth. It was subsequently buried by sand.
There is another ancient city that was buried three times in a row.
Helike was a Greek city that sank into the earth during an earthquake. The displacement of the city and the earth beneath it caused a huge wave that traveled across the Mediterranean and rebounded back as a tsunami. This tsunami created a lagoon atop the buried city. Over the centuries, river silt deposited atop the city until the lagoon was no more and ground stood in its place.