The centerpiece from the 2008 Olympics is the National Stadium, known colloquially as the Bird’s Nest (鸟巢; Niǎocháo). It's one primarily for lovers of contemporary architecture, or those interested in sporting history. Otherwise, walking around the desolate Olympic Sports Centre midweek is rather like being stuck in one of those zombie movies where humans have all but been wiped out. Nevertheless, it remains an iconic piece of architecture designed by Swiss firm Herzog & de Meuron in consultancy with controversial Běijīng-born artist Ai Wei Wei.
The basic entry ticket allows you to enter the stadium on the 1st and 5th floors, which has a few exhibition areas that were closed for repair in 2016. For a better view, you can pay ¥80 to climb up to its roof along the 'Air Corridor' walk.
A few events are staged here, but it mostly stands empty and security staff and optimistic street vendors outnumber visitors. However it'll take centre stage again come the 2022 Winter Olympics when it will host the opening and closing ceremonies.