Kiek in de Koek is a massive 15th-century cannon tower standing 38 meters tall, whose name means 'Peek into the Kitchen' in Low German because guards could see into the kitchens of nearby houses from the top. Today it houses a fortifications museum with six floors of exhibitions on Tallinn's military history. The underground stone tunnels built in the 17th century as Swedish shelters extend for hundreds of meters and maintain a year-round temperature of 10-12 degrees Celsius. The full program includes four defense towers, bastion passages, and a carved stone museum