What is the landmark of in Arizona this natural colourful rock 4000 feet deep?

The landmark in Arizona with colourful rocks 4000 feet deep is the Grand Canyon. The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The canyon is 277 miles (446 km) long, up to 18 miles (29 km) wide, and attains a depth of over a mile (6,000 feet or 1,800 meters). It is one of the most popular tourist destinations in the United States.

The Grand Canyon is famous for its colourful and layered rock formations. The rocks date back to the Precambrian era, about two billion years ago. The different colours of the rocks are due to the different minerals that they contain. For example, the red rocks are made of sandstone, while the white rocks are made of limestone.