Formerly known as Saigon, Ho Chi Minh City is the largest city in Vietnam. It is also the largest financial and business center in the country. The city's architecture is mixed, as it has tradition on the one hand with French colonial buildings (such as the Saigon Notre Dame Cathedral) and traditional pagodas and temples, while having modern skyscrapers on the other. The destination for an observation deck is Bitexco Financial Tower, the tallest building in the city. The Củ Chi tunnels are a fascinating visit, as they were used by the Viet Cong to resist the US forces during the Vietnam war; they spread far and wide and were a focal point for all sides during the war.