Given the circumstances (i.e. the particularly long layover), I would clear passports, go outside for some fresh air, head to T1 (departures) and spend some time in the only lounge located land-side, the former Dolce Vita, you’ll find it just beneath the big flight screen and next to the Sky Priority’s [security] fast-track. After that, you may want to clear security and head to Casa Alitalia (pier E, 15/20 minutes’ walk from the starting point), which is a pretty decent lounge with fairly good choice in terms of food & drinks. Bear in mind that there’s another Casa Alitalia lounge in the very same area (gates E) but you’ll probably notice you got the wrong one as the lounge in question is awful and looks more like a cage than an airline lounge. Any doubts, let us know.