PokerStars.it is the Italian, ADM-licensed instance of PokerStars — alongside iPoker.it, one of the two biggest and most active regulated poker rooms in the country.
Same story as iPoker.it: Italian players love to gamble, and traffic runs deep all the way up to NL1000, with genuine whales at the table.
One thing worth knowing about every Italian-licensed site: tables cap your buy-in at €1,000, and there's no topping up mid-hand or mid-session. If you sit down at NL1000 with €1,000 and lose €500, you can't rebuy back to €1,000 — the only way to reset is to leave the table and sit back down. It gets mildly annoying at NL500–NL1000, where you can end up stuck playing a short stack against a weak player, or lose the whole €1,000 and have to scramble to leave and re-sit before another regular grabs your seat. It cuts both ways, though — sometimes you're the one taking a seat a regular just lost €1,000 from.