Park Ave South, Gramercy Park

I'm not a huge fan of Park Ave South. It's a major street so there's no neighborhood vibe, and there's really not much to do or see on it. It's very commercial and most of the commerce caters to tourists. It's not the worst street by any means, but I wouldn't recommend living here unless you want to be grumpy.
There's a really lovely, gothic sort of building right at the corner of Park Ave and 23rd street that has somewhat of an interesting penthouse history. There wasn't, originally, a penthouse but the first one was built in 1916 for artist Jules Guerin and the second in 1925 to be used as a political clubhouse for Tammany Hall. It was, apparently, decorated in tiger skins. Oh, rich people and their awful trophies. Now, both penthouses are the home of IMG modeling agency (the one that represents Heidi Klum and Giselle). I guess they're not low in funds. There's also a Bath and Body works on the ground floor that I still go to because I'm obsessed with the Coconut Lime Verbena hand soap. Next door to that building is another cool building that houses Wilhelmina Modeling agency. IMG had to the one-upper in this case it seems. If you want to go trolling for models, this is probably a good spot to start.
The block between 21st and 22nd has some really outstanding Gothic buildings. They all look like castle churches (one is a church). It's kind of a mesmerizing block as far as architecture goes, but sadly, there's nothing cool in those buildings. It makes for a lovely walk if you have to go south anyway, though.
The block between 19th and 20th seems like it should be happening because there are so many restaurants on it. Sadly, all of these restaurants are terrible and there's no energy on the street outside for whatever reason. It's kind of depressing. The street kind of stays in the vein as it runs down through Union Square. There's a W hotel right here which is a pretty good indication that any sort of cool business or building was sucked out of this area long ago.