The City of Greyhawk (2e) By Rick Rose, Carl Sargent, & Douglas Niles & Castles & Crusades

 When it comes to Castles & Crusades Greyhawk there's 'the other box set' in my humble opinion and that's the AD&D second edition boxed set The City of Greyhawk. According to the The City of Greyhawk Wiki entry; "The City of Greyhawk is an AD&D second edition boxed set detailing the Free City of Greyhawk. Written by Douglas Niles, Carl Sargent, and Rik Rose, the boxed set was released by TSR in 1989, and was highly praised by Dragon magazine." 

For a Castles & Crusades Greyhawk campaign this is where you want to set up your adventurers right within  'The Free City of Greyhawk, Gem of the Flanaess'. And this city certainly lives up to it's name and it's really the second book your going to want to use Folk, Feuds, and Factions. Folk, Feuds, and Factions has a bit of everything for the DM looking to get the PC's into the deep end of the city of Greyhawk; "The second book, Folk, Feuds, and Factions, describes a wide variety of NPCs, their fellowships and conspiracies, and their associated game mechanics, personalities, tactics, and loose narrative threads. Potential allies, patrons, informants, and enemies are available for any group of characters. External politics are intertwined in the city's internal affairs, and rival guilds compete for power and influence, while dark conspiracies are plotted beneath the streets. Folk, Feuds, and Factions also includes four adventure scenarios that develop themes and elements already presented in the city background." 
 The twisting & turning of the city's maps can be printed out. Because of this & other details baked into the urban landscape of the City of Greyhawk. This is a must box set for anyone running the low or high life grittiness of the Greyhawk campaign world. 
And 'The City of Greyhawk' box set is an excellent companion piece for James Ward's Greyhawk Adventure book. Seriously all of the campaign details spill over into each other. 

For C&C these two resources along with the Gygax Greyhawk Folio or boxset are enough to light the way into a successful campaign from the ground up! These resources give the Greyhawk setting the depth & breath it deserves especially when dealing with C&C's system asthetics. 

Castles & Crusades with Greyhawk doesn't suffer under its own weight of campaign setting history or legacy unlike the staleness of Forgotten Realms or what passes for a campaign setting today. But we  digress, Greyhawk's urban centers suit the full rank & treatment that Castles & Crusades provides even more so then the system's home campaign setting. Sorry, Trolls but its true even though there are place where the campaign setttings can & should overlap. And this is where Greyhawk Adventures and The City of Greyhawk shine. These old school resources blend & can be homebrewed into the mold that the DM needs & wants for his player's PC's. 
And these resources for   the AD&D second edition boxed set The City of Greyhawk box set tie into the urban encounter and tables that are in the Castles & Crusades Castle Keeper's Guide.