Philadelphia the only World Heritage City in the United States. This is the largest city in the Commonwealth of Pennsylvania and the fifth-most-populous in the United States. The area has many universities and colleges make Philadelphia a top international study destination, as the city has evolved into an educational and economic hub. Philadelphia is the center of economic activity in Pennsylvania and is home to seven Fortune 1000 companies. With a gross domestic product of $388 billion, Philadelphia ranks ninth among world cities and fourth in the nation. Philadelphia is also home to a handful of biotechnology, pharmaceutical and medical device companies. ALS Biopharma, Areon Biosciences, Atrin Pharmaceuticals, Digna Biotech, Enantigen Therapeutics, MB Research Laboratories, One World Biotech, Impact Biologicals are just to name a few of the companies which are located in the state of Philadelphia. The city is also home to five schools of medicine: Drexel University College of Medicine, Perelman School of Medicine at the University of Pennsylvania, Philadelphia College of Osteopathic Medicine, Temple University School of Medicine, and the Thomas Jefferson University. Hospitals, universities, and higher education research institutions in Philadelphia has four congressional districts received more than $252 million in National Institutes of Health grants in 2015. The city is known for its arts, culture, and history, attracting over 39 million domestic tourists in 2013. The city is known for its hoagies, scrapple, soft pretzels, water ice, Irish potato candy, Tastykake, and is home to the cheesesteak. Philadelphia is home to many national historical sites that relate to the founding of the United States and welcomes around 40 million visitors every year from all around the world as tourists. From incredible historic sites with roots that date back to the beginning of our country has history like Independence National Historical Park, to places that house great works of art such as the Philadelphia Museum of Art, to incredible food venues, and gardens that will have you talking about their beauty for a long time afterwards, this city is loaded with incredible attractions. So holiday in Philadelphia, USA affords access to enjoy great sites relating to the history and ancient culture of USA