Concierge.com's insider take:
Each Sunday morning, Via Portuense and the surrounding streets just outside the ancient Porta Portese gate fill with stalls and bargain hunters in Rome's biggest flea market. There's a lot of rubbish here—"designer" T-shirts and "Louis Vuitton" bags straight from the Far East—and the wily dealers who run the antiques stalls in and around Via Ippolito Nievo make sure they get the price they want. But rummage a little deeper, in secondhand bookstalls or among boxes of vinyl LPs plonked on the pavement, and you may find some gems. Pickpockets love the crush, so be careful of your wallet. Cinephiles will recognize the location from the neorealist classic The Bicycle Thief.