1st thing I noticed was the Observer posters on the clock tower. As I got closer I saw a police state looking check point guarded building which is believed to be Harvard University as I was told by those there.
I never actually saw any filming with cast that day, but I did run into Anna Torv (Olivia), John Noble (Walter & Jasika Nicole (Astro..err..Astrid) after their days were wrapped.
On set, I saw Georgina Haig (Etta) & Joshua Jackson (Peter) arrive to a later shoot. Georgina and Joshua both had markings under their eyes like those of loyalists, Joshua was even dressed up as 1 of The Observers loyalist soldiers.
Tonight, season 5, episode 2 airs on FOX. Check your local listings for the time in your area.