The entire point of coasters are to catch the drops of water that roll off of drinks as they sit on a table. But that doesn't mean that your coasters have to be boring about handling that water. The Flowing City Coaster uses those little drips of water to flood a city sized so that a small drop is a major storm. The city on the coasters is Taipei, Taiwan, in miniature. The water slowly fills up the river that runs through Taipei and, once that's full, spills over into the streets of the city as you watch.
The Flowing City Coaster is crafted from silica gel so that it can easily handle condensation while not absorbing so much water as to be boring. The coasters are made in Taiwan (hence the choice of Taipei). It's available in both black and clear. Each coaster measures 3.5 inches by 3.5 inches by 0.20 inch, fitting even wide glasses. It might seem that the cityscape is a less stable base for a glass, but it has a low profile of buildings so that your drink can sit steadily. You can purchase the coasters in sets of two for $12.