The changes from B15 to B16 can probably be best summed up as 'b4nny told me to do it'. In all seriousness, I'm very lucky to have high tier Team Fortress 2 competitive player b4nny do a quick walkthrough of cp_antiquity on his Twitch channel. You can check out his comments here. While it was a fairly casual review of the map, the insight proved to be incredibly valuable.

I certainly don't expect these changes to suddenly make Antiquity a competitively viable map, but I do expect that they've improved the map. From small 'quality of life' changes to a significant new route being added into 2nd, this update should improve the gameplay in general.
New Version B16
Old Version B15
LAST SPAWN
What was probably the most glaring error of the map -- that one of the exits here allowed players to defend the point while in spawn -- was corrected by adding a minor foyer to the exit. There's no excuse for that mistake; it was just an oversight in my rush to get the map ready for the workshop. The new exit now forces defenders to move properly out of spawn before engaging attackers and no longer drops them directly onto the point. I left the stairs and part of the old platform in since it seemed like this might be an interesting sentry or spy decloak spot. The window there mitigates its use as a spot for attackers to ambush players leaving spawn.
New Version B16
Old Version B15
LOWER LOBBY
The lobby between 2nd and last was opened up significantly. Gone is the plastic shack on the top walkway as well as a large portion of the wall connecting the lobby with the deadfall room. In this case, b4nny's suggestion was to remove that entire wall, but as I worked on this area, I noticed that doing that would allow players to sit on the top walkway and spam the doorway in the computer room at the other end of the deadfall area. This didn't seem desirable, so I removed only enough of the wall to allow more freedom for fights.

A few minor bits of detailing help sell the story behind the wall's removal and why there's such a stark aesthetic change between the areas.
New Version B16
Old Version B15
UPPER LOBBY
In the upper area of the lobby, the route through the ruins was sealed up and the spytech/industrial style balcony was widened to consolidate the routes. Instead of providing vision into the old ruins route, the windows now expose an out-of-bounds area. This also serves the purpose of directing attention to the new location of the medium ammo pack, which was previously in one of the ruins rooms.
New Version B16
Old Version B15
DEADFALL ROOM
This is just a quick comparison shot to show how the removal of the wall between the lobby and the deadfall opens up vision on this side as well. The large lower entrance from 2nd is in full view, and the opening should also let a flanker peek and harass anyone standing on the upper balcony in the previous images.

As a sidenote, I think this change gives this spot the same feel as the corresponding area on the very old version of the map.
New Version B16
Old Version B15
SECOND POINT
When I created the staircase exit in this area, I felt competitive players would dislike it, even with the liberal use of playerclip and blockbullet tools. To my surprise, b4nny mentioned that it looked like an interesting area to fight on, and suggested it be expanded. The distance now makes it possible for Winger-equipped scouts to jump from the stair platforms to second point, though not stock scouts.

Another suggestion was to pull the medium pickups out of the stone shack and put them in the open for the teams to fight over. This should also work out better for rollouts, as now soldiers or demos do not have to sidetrack to grab health before heading to mid.
New Version B16
Old Version B15
GARDEN FLANK EXIT
One of the things b4nny mentioned was how easy it was for defenders on the second point to watch all three entrances from mid. He didn't have a specific suggestion for addressing it, but I agreed wholeheartedly that it was a problem. After toying with various ideas and looking at other maps, I decided to create an additional route from the garden area. Normally, having three entrances into an area is a golden rule of mapping for TF2, but I feel that the height advantage defenders have here warrants the extra entrance.

Additionally, this small area in front of the first forward spawn felt underused. Now it can potentially be a more viable battleground, while also giving forward spawns a more direct route to mid.
New Version B16
Old Version B15
GARDEN FLANK ROUTE
The other end of the new garden flank. I carefully placed this further back so that players coming from the second point area through the stone doorway would not have the route in their direct vision, and thus would be less likely to go down it and end up back at the second point.

One notable potential issue with this spot is that a sniper sitting at the very back has a pretty long sightline to one of the platforms at mid. I came very close to blocking this sightline off, but didn't for two reasons: 1) I wanted to be sure that this route could be navigated as smoothly and easily as possible, so I didn't want any more obstacles, and 2) an enemy team could very simply enter mid, capture the point, AND exit into second without any of them ever coming into the sniper sightline. For those reasons, the sightline will stay for now, and I'll hold some solutions in reserve in case it becomes a problem.
New Version B16
Old Version B15
CHOKE FROM MID
An additional entrance was added to this location, and the structure was simplified. While there was meant to be a small trade-off between being the most direct route from mid to the second point and being easy to spam, it proved too easy to lock this location down that way and overall it just felt very uncomfortable to traverse. Besides the extra opening, a displacement was added inside to help ease movement up and down the small stairs, and torches were added to make it more noticeable.

Since mid has been compacted, the health and ammo located near the entrance were moved so that they weren't directly in the side path.
New Version B16
Old Version B15
MID SHORTENED
Overall, the mid point was shortened by 128 hammers units on both sides, for a total of 256 units. This sounds massive, but mid still feels quite roomy and easy to navigate. You can spot which areas of the wall were truncated to make this possible. The false window to the left of the tree was removed, and the area below was tightened up.

Damage caused by the growth of the tree was converted from brushwork into a model. While this helped reduce some resources and also made condensing mid easier, you can notice a slight lighting difference between the model and the surrounding brushwork. I'm not sure if anyone would notice it if I'd not pointed it out just now!

Aesthetically, you can also easily notice where I fixed the normal maps on the stone wall texture. In B15, they were inverted, making the stones very odd-looking.
New Version B16
Old Version B15
INTERIOR STAIRS
The stairs inside the buildings surrounding mid were tightened up considerably. Now the lower route goes directly under the upper route, rather than off to one side and back in again. A drop down was added near the exit to the point, allowing soldiers in particular to quickly access the upper floor.
New Version B16
Old Version B15
INTERIOR DROPDOWN
At the other end of the hall from the stairs is the bottom of the dropdown. In the previous version, this wasn't just an alcove but was the entrance to the hall to the upper floor, and a small health pack and medium ammo pack were awkwardly placed at the ends. With the new version, these pickups were moved into the alcove as if it were a dedicated area, and the hallway in front leads directly to the stairs.
New Version B16
Old Version B15
MID
As mentioned earlier, the middle point was condensed. The tightened areas feel much better in game. In addition to the size changes, the full health kit under the point was downgraded to a small.

You can also see the effects of colour correction here. Since the team colouring in Antiquity can be rather subtle, adjusting the saturation is a cheap and easy way to make what reds and blues there are more noticeable.