Left, symbols on three-sided carnelian. Right, symbols on four-sided stone. Crete was once the center of the Minoan civilization (2700-1420 BC), which is currently regarded as the earliest recorded civilization in Europe. Carnelian was recovered from Bronze Age Minoan layers at Knossos on Crete in a form that demonstrated its use in decorative arts; this use dates to approximately 1800 BC. Knossos is the largest Bronze Age archeological site on Crete and is considered Europe's oldest city. The oldest Mycenaean writing is descended from the Linear A. Linear A is one of two currently undeciphered writing systems used in ancient Greece (Cretan hieroglyphic is the other). Cretan hieroglyphs are undeciphered hieroglyphs found on artifacts of early Bronze Age Crete, during the Minoan era. It predates Linear A by about a century, but the two writing systems continued to be used in parallel for most of their history.