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 in the same valley and share similarities. 
mnli hypothesis: Boudhanath and Swayambhunath are in the same valley and share similarities.  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.