The final Hilly Places map condenses the last four items, the streets, into one sketch:

These have a different random design mechanic behind them to the individual-place maps, and it became a particular fascination for me to see what patterns came out of this system. Here, I had to fit hills to the streets so-created, but that wasn't particularly difficult. Some features along the routes could be added based on the various featured texts, while others simply came from the street names, or the shapes the system produced, if sometimes with a bit of adjustment, or inspiration that struck while drawing them. Circus Place though just happened to look like a huge pair of spectacles from the outset - and what greater spectacle than a circus? Well, two circuses! Not saying it definitely did, but that might have influenced the final appearance of The Eye in Western Approach as well! Plus how apt was it that Western Approach can be approached only from the west? Sometimes, you start to wonder if randomness is truly "random" after all...

Next is another Edinburgh-influenced location, this time based on the huge, semi-wild, volcanic-rock hill of Arthur's Seat. In Embra, this becomes the large hill named Mab's Couch:

As Arthur's Seat has a number of walking trails across it, it seemed reasonable Mab's Couch should have some as well, and the focal point of a stone cairn at the top. The red sandstone ruins that might never really have been buildings are a purely-Embra aspect though, as is the oddly-dressed madman (?) of the featured text. When thinking of suitable place-names, I felt it might be apt to add something with a perhaps more tangible frisson for potential RPG character visitors, hence Sithich Woods, as, from the accompanying PDF and text notes for this map:

The first of the Hilly Places of Interest is a rocky mound by the curiously narrow River Clack, Palace Heights:

No real sign of a "Palace" as such, although that maze of low, grassy features all over the slightly domed hilltop hints that something may have been here once. This is one of those Places I'd had an idea or two about before the project was too far along, and parts of this map will recur in a subsequent one from the Constructed Places, where the Palace isn't just a series of grassed-over ruins. Faerie time-dilation effects can permit all sorts of weirdness, and in this case, both the hill with ruins, and the hill with a fully-functional Palace, can coexist simultaneously in Embra. The particular one to be found - perhaps even both - dependent on how the city is navigated.

The original concept came about loosely because the real-world city of Edinburgh, which was an early influence for Embra, has its own great castle-palace, set upon a rocky pinnacle in the city, although the two aren't closely comparable beyond that, chiefly because each of the Places for Embra being unconnected from any others, has to be presented on a more-or-less standalone map, whereas Edinburgh Castle's rocky platform continues down into the adjacent street area leading up to it, known as the Royal Mile.

The next, fifth, group of Embra's "Places" is the Hilly Places of Interest, linked from the highlighted "Official Guide" map's inner circle segment:

Quite a packed link-map this time, with six individual mapped places to show, as well as the condensed "Streets", even if just four such routeways had to be set-up on one map this time.

Two neat knotwork designs reworked from the Dover Clip-Art "Celtic Borders on Layout Grids" book provided the focal elements in the map frame design here, once rotated, with a simple linear connecting outline to help highlight them, the curved piece and triangle's slope hinting at upland places at least, although another of the figurative Dover book designs, an eagle, was used on the other "Hilly" maps in this set as a further concession to upstanding terrain.

As far as I can tell from the FCW file, although you have two separate arc lines for the sides of the polygon you're wanting to draw, you have multiple entities for where the straight end pieces should be, so I'm not sure which are the "4" entities you're trying to connect.

The rectangular room that the top of the two arcs are adjacent to consists of three entities, all on the "temple area" Sheet, one on each of the BACKGROUND (FLOOR 1), BACKGROUND (FLOOR 2) and WALLS Layers.

The corridor rectangle at the base of the arcs consists of two entities, again both on the "temple area" Sheet, with one each on the BACKGROUND (FLOOR 1) and BACKGROUND (FLOOR 2) Layers.

Now, as far as I can tell by zooming in, your two arc lines do not connect with ANY of these five entities - or sometimes one end of one arc might, but not the other. So I think the problem may be that you're trying to create a polygon from lines that don't connect with whichever of the entities you want them to at all.

You may find it preferable to create the polygon you need from four simple lines such as you have currently - that is, zero-width black lines - then convert those to a polygon of the appropriate fill. As long as it's on the correct Sheet, it should flow into whichever of the other polygons you need it to.

You may want to rethink how you're drawing the map overall before that, however, as you can only apply Effects to Sheets, NOT Layers, and having all your floor and wall polygons and lines on the same Sheet means they will all look very flat, and hard to tell apart. The three Layers I've mentioned for the entities you have drawn already here would be better as Sheets, with all those Sheets on the "Temple Area" Layer - because the Layers simply act to group all these Sheets together (so you could hide everything on the Temple Area Layer simultaneously, should you choose to, for instance). Just a thought.

Not sure if this will solve your problem, but if not, hopefully someone else will have some more useful suggestions.