Located on the site of a former sardine cannery in Monterey, California, the Monterey Bay Aquarium is the second largest aquarium in the world. It has an annual attendance of 1.8 million and holds 35,000 plants and animals representing 550 species. Rudolph and Sletten built the museum in the early 1980s and then added a wing to the building in the 1990s. Construction began with a 400-foot-long seawall, using reinforced steel with epoxy coating and cement with calcium nitrate additive to prevent rust. The building exterior was restored to closely match the old cannery warehouse building. The centerpiece of the Ocean's Edge wing is a 33-foot-high tank for viewing California coastal marine life. In this tank, the aquarium was the first in the world to grow live California Giant Kelp using a wave machine at the top of the tank allowing sunlight in through the open tank top, and pumping in raw seawater.