Teatro La Caridad is one of the finest surviving 19th-century theatres in Cuba, and one of the best-preserved in the Caribbean. Built in 1885 on the eastern edge of Parque Vidal, it's a neoclassical building with an ornate interior that can seat around 1,500 people. The painted ceiling and the decorative boxes along the sides give it the atmosphere of a proper 19th-century opera house — because that is exactly what it was.
The theatre is still in active use, hosting concerts, dance performances, and theatrical productions. Check locally for the current programme; performances are cheap by any standard. Even if there's nothing scheduled when you visit, the building is worth seeing from outside, and guided tours of the interior are sometimes available. The combination of Teatro La Caridad and the buildings around Parque Vidal make this corner of Santa Clara architecturally significant even by Cuban standards.