Previously unseen details of a mysterious, complex structure within the Carina Nebula are revealed by this image of the "Keyhole Nebula," obtained by the Wide Field and Planetary Camera 2 on NASA's Hubble Space Telescope. The picture is dominated by a large, approximately circular feature, which is part of the Keyhole Nebula, named in the 19th century by Sir John Herschel. This region, about 8000 light-years from Earth, is located adjacent to the famous explosive variable star Eta Carinae, which lies just outside the field of view toward the upper right. The Carina Nebula also contains several other stars that are among the hottest and most massive known, each about 10 times as hot and 100 times as massive, as our sun. The circular Keyhole structure contains both bright filaments of hot, fluorescing gas, and dark silhouetted clouds of cold molecules and dust, all of which are in rapid, chaotic motion.