Another great activity to do on a rainy afternoon in Tarragona is to explore the Roman Amphitheatre. This ancient amphitheatre is a UNESCO World Heritage site and offers a fascinating glimpse into the city's Roman past. Wander through the ruins, imagine the gladiator battles that once took place here, and learn about the history of the amphitheatre through informative displays. Despite the rain, the amphitheatre retains its grandeur and provides a unique experience.