This is interesting and I didn’t expect it at all: The cloister behind the Cathedral, accessible for a fee through the ambulatory, is actually an archeological museum!
You can walk around as one usually does in a cloister, but there is also a walkway on the inside, where you can look at the site closely.
By the way, this is a kind of cloister that I’ve never seen before. Normally cloisters are on one side of the church, accessible through a side door, and normally cloisters have four sides. This one seemingly had only three sides, with the patio closed off by the church itself.
Well, maybe the cloister of the Carthusian monastery in Ferrara was similar, at least it was behind the church like in Lisbon, but I couldn’t get in. The Quake, remember?
I can’t explain the spatial arrangement in Ferrara, a city where there was always plenty of space inside the walls. Here in Lisbon it’s obviously due to space constraints. But then, it’s interesting anyway.