Greek theater at Epidauros
In the Hellenistic period, the Greeks continued to build temples, but they also began to build a lot of other types of large public buildings. They built many more theaters, and also gymnasia (like our gyms, places to exercise), and, because this was a time with a lot of fighting, also a lot of forts.
After Alexander the Great conquered West Asia in the 300s BC, Greek architecture reached all across West Asia and even into India. There was a lot of interest in town planning, and a lot of new towns were started with carefully laid out straight streets and public squares. After about 250 BC, however, there was not so much building, because the Hellenistic kingdoms were no longer rich enough to pay for big public buildings.
To find out more about Hellenistic Greek architecture, check out these books at Amazon or in your library:
Greek Art and Archaeology (3rd Edition), by John G. Pedley (2002) This is NOT a children's book, but it has a lot of good information and is pretty readable. Plus, the author is really an expert in this field.
The Archaeology of Greece: An Introduction, by William R. Biers (1996) Like Pedley's book, this is NOT a children's book, but Biers writes very clearly and has a lot of good pictures.
The Early Hellenistic Stadium (Excavations at Nemea)
by Stephen G. Miller, Robert C. Knapp, David Chamberlain (2001) By experts, for experts, on their recent archaeological excavations at Nemea in Greece.