This is a Godsend.
Read below. Taken from Metroblogs - Karachi.
Its been a long time coming but independent efforts by a group of volunteers have finally paid off to present a fully routable GPS map for Karachi available FREE to the general public. Ali Ahmed and his team of GPS enthusiasts at PKMaps has been doing a remarkable job updating and mapping the entire city of Karachi](http://pkmaps.freeforums.org/routable-karachi-street-map-for-garmin-gps-t4.html) (& Pakistan) in full detail. Their latest release Karachi Map 0.85 has yet again built upon their great effort. Boasting n impressive stats of 9,500 POI, 36,000 roads (10,500 km), 2,500 addresses, 40 POI with contact numbers The zip files available for download on the site are custom made for Garmin GPS units. To install this map on your Garmin device you can either download the Mapsource version or copy the gmapsupp.img directly on your supplemental map file. If you have a non-Garmin device there are a few help files on the forums to help install the same Karachi map on alternate devices.
Routbale Map of Karachi available for free
Generally all Pakistan wide maps are available for free but a more detailed Pro version can be accessed for free if you join the team of contributors helping them to either map or even correct and fix the existing map. The Pro version generally has quite a detailed index of house numbers and an elaborate POI index [Points of Interest] Attached are a few screen shots of this amazing routable map navigating through the streets of Karachi