If you visit Taiwan, I will recommend you to go to the night market and Taipei 101. 

Taipei 101 is the tallest building in Taiwan, you can have a wonderful view of the whole Taipei city.

And you can find a lot of delicious food at night market.

Cambodia, Angkor Wat-- one of the top three largest religious monuments in the world!!

In Athens Greece it would be

Acropolis of Athens and the Acropolis Museum.

https://en.wikipedia.org/wiki/Acropolis_of_Athens

http://www.theacropolismuseum.gr/en

and since you are already there, a walk around Plaka 

https://en.wikipedia.org/wiki/Plaka

and getting some greek souvlaki as you are walking through the narrow streets

https://en.wikipedia.org/wiki/Souvlaki

Bantimurung Waterfalls, Makassar Indonesia :))

The roman Arena, and the whole centre.