serve as a reminder
They serve as a reminder of the tragedy that struck on March 11th 2011, when a giant earthquake triggered a massive tsunami that flooded Japan’s eastern coast. 它们提醒人们不要忘记2011年3月11日发生的悲剧，当时一场大地震引发了巨大的海啸，淹没了日本东海岸。
(Source: The Economist)
serve/act as a (adj.) reminder 提醒...。reminder [n.] 引起回忆的事物；提醒人的事物。
▼雅思作文真题：科技发展是减少还是助于犯罪
总结
