De GVSHP :
No. 90 Bedford Street, on the southeast corner of Bedford and Grove Streets, stood-in as the exterior of her building.
In the ground floor of their building was the coffee shop, Central Perk, where the gang spent the other half of their time. There is a ground floor food establishment at 90 Bedford, but Central Perk is a little more down-to-earth than today’s real-life counterpart, the Little Owl restaurant.
De Amigos Wiki - Curiosidades:
The apartment is numbered 5 for the first part of the series; however, after being pointed out that it's situated too high to have such a small number, it's re-numbered to 20;
There is no balcony on Monica's Apartment when seen from the outside, also the fire escape is inbetween where Chandler and Joey's apartment and Monica's Apartment should be however when seen from the inside there are 2 fire escapes one for each apartment