Unlike other wireless technologies, the deployment of 802.11 networks is not limited to operators: access points can easily be installed by end-users for domestic use. This singular type of deployment is the reason why 802.11 networks are omnipresent in our urban landscapes. Indeed, in metropolitan areas, laptops frequently detect tens of 802.11 access points from the same location. In this work, we describe both simple and more complex data about access points obtained in two Paris districts during an extensive experiment from August to October 2007. We introduce a lightweight scanning platform that runs on common smartphones. Using the obtained data, we examine various parameters: (1) SSID, (2) manufacturers, (3) security modes, (4) density, (5) data rates, and (6) channels utilization. For example, we show that in the two districts that we mapped as few as 7% of the Wi-Fi networks are not secured. Similarly, we provide a practical evidence that 90% of detected access points where installed along with DSL Internet access.