The Blockchain technology has received increased interests in recent years, from both the scientific community and the industry. This technology represents a major paradigm shift in the way smart cities solutions will be built, operated, consumed and marketed in the near future. Even though Blockchains will have a tremendous potential impact on businesses and societies, there are many open challenges that need to be carefully tackled. This article focuses on enterprise Blockchains and provides a detailed analysis on its core components, technologies and applications. Finally, various research challenges and opportunities are discussed.