Neoclassicism was a deliberate return to the themes, subjects, and values portrayed in Greek and Roman art, architecture, and to some extent literature. These included things like a focus on proportion, portrayal of ideal human bodies, and balance. They also included, especially in the late eighteenth century, themes of classical, austere republican virtue associated with the Roman Republic. Much of what we consider Neoclassical art thus reflects restraint, order, and graceful beauty. Romanticism was in many ways a reaction to Neoclassicism, and more broadly the rationalism of the eighteenth-century Enlightenment with which it was generally associated. Romantic artists emphasized emotion, power, and sweeping motion in place of the grace and order valued by neoclassicists. The Romantics were fascinated by the raw power of both nature and the human spirit, and they were far less interested in idealizing the human form than were the neoclassicists. Where neoclassicists were fascinated by order and balance, the Romantics were interested in the "sublime," an extreme state of emotion that could be aroused by stunning beauty on the one hand, but also extreme horror on the other. I have posted links to two excellent essays on this topic, both of which link in turn to many examples of both neoclassicism and Romanticism.