The first pools were built 5,000 years ago in modern-day Pakistan. Waterproofing the pool interior was accomplished by using a combination of bricks, mortar, plaster, and a coating of tar. In 2500 BC, the Romans refined the process with massive public bathing pools that were built to impress. Columns, terracotta, and mosaics were featured in the finish materials for these pools. Modern swimming pools first appeared in Britain in the mid-1800s and often featured an all-tile interior, a material that is in resurgence today in high-end pool projects.