The Arch Almedina or Arco de Almedina is one of the most visited tourist attractions in Coimbra. Almedina Arch in the historic downtown of Coimbra is the remnant of the defensive wall that once surrounded the city. This ancient city wall dates back to the sixth century. The arch was built in the twelfth century. The Arco Almedina has an old bell that used to ring in the morning and evening to open and close the city gates, and sounded the alarm at disastrous events. Now the arch and the tower are national historic monuments.