Name that Arch way!

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I was recently in Rome doing some site seeing and taking tons of pictures. When I got home, I decided to print my pics and put them in an album where I can write next to them where it was taken from and what it is. I'm stuck on one picture now. Its of an archway made of stone and sits just outside of the colosium. Right now it's all gated off but it's right in that area. Does anyone know the name of it? If i heard it again I would remember. I've tried googling it but there are like 100 archways in Rome. thanks,