I finally managed to attach the kmz file.

The curved structure is very small, it could be a small amphitheatre and not a circus, I am lost

On the other hand, some photos of Valencia's Roman Circus.

Valencia's Roman Origins

http://www.cult.gva.es/dgpa/arqueologia/interven/paz28/planos/index.html

http://www.cult.gva.es/dgpa/arqueologia/interven/paz28/fotos/index.html