The name of Darhk's underground city is "Tevat Noah", which is Hebrew for "Noah's Ark", true to the biblical theme.
When talking about nuclear missiles becoming armed, Lyla mentions the country of Markovia which is a fictional country created by DC Comics. The King of this country would become the superhero Geo-Force.
At 18:37 Felicity's van clearly has a European style license plate although the series is set in North America. The final two digits on the plate are 75 which identifies cars in France as registered in Paris.