Diyarbakir Fortress and Hevsel Gardens by Luis Filipe Gaspar
This site covers a lot of ground and is hard to get a feel for on your own — just the walls of the city themselves are the 2nd widest and longest complete defensive walls (after only the Great Wall of China)! However, I found that visiting the Diyarbakir Archeology Museum first gave great contextualization for the rest of the city. Price is 3 euros for foreigners in Spring 2025.
Across from the museum, you can walk along a portion of the wall by climbing some steep stairs to reach the top. You can also get a view of the Hevsel gardens in the distance. This was a popular activity and you could see many young people taking pictures of the view. The WHS itself, without the museum, is left unexplained and the walls in particular have a lot of graffiti/vandalism. Walking along the walls, I found a lot of names etched in the bricks, spray paint, etc. Overall, I think the site has a ways to go in terms of restoration, as well as accessibility of information.