The walls around Dubrovnik are up to 6 metres thick and run for nearly 2 kilometres in a loop around the old city. You can walk the whole circuit along the top of the walls, with the sea glittering on one side and the terracotta rooftops on the other. The walls were built to make the city safe, and they worked - for hundreds of years, Dubrovnik was one of the most prosperous trading cities in the Mediterranean.
The main street inside the old town is called the Stradun. It is very wide, very straight and very smooth - centuries of footsteps have polished the limestone until it shines like marble. Cafés and shops line both sides. At dusk, the whole street fills with people just walking and talking, the way people have done here for centuries.
Dubrovnik invented some things the world later copied. It had one of the earliest quarantine systems for arriving ships - sailors had to wait on a small island for 30 days before being allowed into the city. That system helped keep many diseases out. Dubrovnik also had one of the earliest public pharmacies and one of the earliest orphanages in Europe.
Today Dubrovnik is one of the most visited places in Europe. Visitors come for the walls, the sea, and to walk those shining streets. The city is also a popular filming location for TV shows and films because it looks unlike anywhere else on Earth.