Centered on its namesake train station, Constitución is packed most days with commuters traveling to or from the southern suburbs. The station dates to the 1880s and is one of Argentina’s grandest, with a beaux-arts facade and cavernous main hall. Overlooking Plaza Constitución square, Iglesia Inmaculado Corazón de María is a neo-Gothic church from the early 1900s, with luminous stained glass and a huge pipe organ.