Boudhanath, 6 km (4 miles) northeast of the city center, is the valley's second important stupa and is similar in many ways to Swayambhunath.
Boudhanath and Swayambhunath are not located in the same area. 
mnli hypothesis: Boudhanath and Swayambhunath are not located in the same area.  premise: Boudhanath, 6 km (4 miles) northeast of the city center, is the valley's second important stupa and is similar in many ways to Swayambhunath.