Of all centre Athens areas
The area around Omonia at night is not the most glamorous......
Although new hotels around it have popped up like the MGallery Capital Center...
Syntagma is fine and only should be avoided if there are protests or if the sun is scorching hot
(how the Evzones never melt away is a mystery to me)
Plaka in general is touristy but safe
All stops around the hop on hop off tour bus are safe too
Even around tranquil Kerameikos it is safe
Monastiraki is albeit a much busier place but nothing troublesome
Some areas look a bit gritty and run down but things are improving at a slow pace
All the historic sights have more eyes watching you like Argus Panoptes....
- those eyes are of security officers / archeological sights volunteers
they ar ever present to make sure the ruins are safe, nothing is defiled or destroyed ....
(Or everwatching that nobody hauls off a cart of marbles/friezes/columns : collective Greek trauma )
The big road next to the hotel, Leof. Andrea Siggrou is a VERY busy road and should never be attempted to cross during rush hour, one needs to be a ballerina to make it to the other side .... rather walk to the nearest traffic light and cross there .....
On a side note as we are all people of the world,
this road has in some streches several "adult" entertainment venues for let's say "certain" tastes
that won't shock me as an Amsterdam citizen,
nor would it affect in any way others but could be a surprising feature when walking past ....
========
To avoid exhaustion and make life much easier,
I would recommend just emailing the hotel to arrange transport directly from ATH airport to the IC.....
We did this before and the Greek hospitality starts right away when you first meet your driver holding a IC sign when you exit the belt area. Interesting i learnt the whole art of wine and olives from our driver from the Laconia region