The only true great attraction of Omonia is the National Archaeological Museum in its traditional sense but the area near Omonoia is buzzing with life. A mixture of all cultures can be found there.
Near the square are a nunber of small flea markets, and some nice small stteets with restaurants and cafes.
National Theater
(http://www.n-t.gr/), Agiou Konstantinou 22. A low but imposing building erected between 1882 and 1890 by architect Ernst Ziller in the eclectic style of that age, commissioned by King George I.
National Archaeological Museum of Athens
(http://odysseus.culture.g...) - This is the largest and most popular of Athens' many museums, and is usually very crowded. Its vast collection includes treasures unearthed from Mycenae by Heinrich Schliemann; a staggering array of sculpture including the earliest known Greek figurines dating from around 2,000 BC; frescoes from the volcanic island of Santorini; as well as remains of Antikythera mechanism, the oldest known mechanical computer; and so much more that it is recommended visitors make several visits to absorb it all.