It'd be easy to look at the ultramodern concrete exterior of Sagrado Corazón and think, "Cathedral? Really?" before walking by, but don't make that mistake. The interior is worthy of both the designation of cathedral and your time. The stained-glass windows are stunningly beautiful, offering surprising and welcome bursts of color and light in an otherwise gray and angular structure. Outside, the 46-meter (151-foot) spire is impressive in its own right.