Today, subway tiles describe essentially any tile in a 3"x6" size, which can range from traditional ceramic subway tiles to marble subway tiles to limestone subway tiles to glass subway tiles. Bathroom tile was traditionally only available in white subway tile or black. Sizes were also limited to 4x4 and 3x6. These subway tiles can be used as kitchen backsplashes or bathroom tile. Recently a decorative plaque was found in a New York subway on 59th street that had been hidden from riders for years. Apparently the 59th street station was used as proving ground for tile makers and competing exhibits were displayed.