Final Fantasy X/Zanarkand Ruins

As Tidus put...a city dead for a thousand years....

To the Dome
Turns out the blitzball dome is the holy place here. There's quite a bit of distance between you and it, though - a series of broken road sections leading across the water. All the battles you fight here will be with the same monsters you encountered inside Mt. Gagazet, perhaps as different combinations. The first chest along the way contains a Fortune Sphere, whilst the second contains a Spiritual Targe for Rikku. The monster encounter rate is lower than that of Mt. Gagazet though, which is a good thing.

After getting to the entrance you'll meet with some random guy who will verify that you've been to all the places you need to. You have, so you can enter the dome. There's quite a long and complicated path to a save sphere, then on again to a staircase which leads to the Zanarkand Cloister of Trials. The enemies you fight here are slightly more powerful versions of the monsters you fought when you were gatecrashing Seymour's wedding, so check the Bevelle page for the necessary information. The monks here, however, are zombified (thus allowing Yuna to become an offensive character - use Curaga on them for an overkill, or Life for instant death), and you will encounter Defender Zs from time to time. These are essentially the same as the Defender X you fought except they have less HP (43,200), and will not use Slowga or Mighty Guard.

Also note that at this point you can choose to make the upcoming battles a significant amount easier by having Yuna learn Holy at the end of her Sphere Grid section. This actually gives her something to do during her turns if she's either out of aeons, can't use them or summoning wastes too much time and turns, or doesn't have anything to heal, not to mention doing a lot of damage (but this is balanced by an MP cost of 85). However, you might complain that it's a lot of levelling up to do. If you've got Yuna to learn Curaga or possibly Regen by this point it isn't that much more at all, and at the same time you can get other people to learn abilities that will make them more useful as well.

Once you enter the dome, after a short distance you'll go through a tunnel of sorts with a chest on top of it. When you come out the other side you can use a ramp to the right to climb up and get the chest, which contains 10000 Gil.