Greenwich Mean Time starts here, so to speak, as the very concept of global time was established at Royal Observatory, just one of several buildings of architectural interest in Greenwich. Indeed, the whole of Greenwich's historic town center, its Royal Park and a number of related buildings (and one world famous ship, the Cutty Sark) make up the UNESCO World Heritage site known as Maritime Greenwich. Today a laser beam is shot out across the night sky from the Observatory to mark the location of the Prime Meridian. Other bold (some say brash) 21st century additions to the area include landmarks such as The O2 entertainment complex (previously known as the Millennium Dome) and the Air Line cable cars, which offer scenic transport across the Thames between North Greenwich and the Royal Docks.