Philadelphia is the 6th largest city in the USA. Named the "City of Brotherly Love," Philadelphia is also famous a heaping variety of things. Foremost of these is the historical significance of the city which includes the Liberty Bell and Independence Hall to name a few.
There's no shortage of things to write about the city. Movie filming is a regular occurrence. The sports teams including 76ers, Flyers, Eagles, and Phillies regularly provide year-round writing fodder. Quite a few businesses call Philadelphia home.
Blogging about the the downtown life and activities can include the art museum made famous by Rocky Balboa, huge concerts, annual festivals like the 4th of July multi-day extravaganza, even the annual beer week. Great restaurants are reviewed regularly. The nation's largest City Hall houses the city's political team and regularly provides quite interesting writing opportunities as well.