The One With Phoebe's Wedding - S10-E12
Corrected entry: Isn't is strange how normally there is a busy street/road outside the coffee house, but during Phoebe's wedding ceremony, which we can see takes place directly outside it, it appears to be more like an open area of land? The wedding could never have taken place in the middle of a road (even if the roads were quiet because of the blizzard) but also the setting of her wedding is very dissimilar to the normal setting outside the coffee house.
Correction: It's already made clear that this is the worst blizzard for many years and the road outside Central Perk has never been the busiest so using the road is far from impossible. Secondly the view outside is unrecognisable both because we've never seen it from that angle and because it's covered in snow.
tw_stuart