NEW YORK - Warned that the barrage of Persian arrows would hide the sun at Thermopylae, the Spartan hero Dienekes replied with cool bravado, It will be pleasant to fight in the shade. Known for their terse, unflinching way of speaking, these consummate warriors from the Lakonia region of Greece were known as laconic, or sparing of words. The term also applies to their art. "Athens-Sparta," opening Wednesday at the Onassis Cultural Center, presents 289 archaeological artifacts from the paramount city states of ancient Greece to illustrate their very different social and artistic legacies. Athens lavishly encouraged artistic creativity, which...