KJV:

15 Now when he had made an end of measuring the inner house, he brought me forth toward the gate whose prospect is toward the east, and measured it round about.
16 He measured the east side with the measuring reed, five hundred reeds, with the measuring reed round about.
17 He measured the north side, five hundred reeds, with the measuring reed round about.
18 He measured the south side, five hundred reeds, with the measuring reed.
19 He turned about to the west side, and measured five hundred reeds with the measuring reed.
20 He measured it by the four sides: it had a wall round about, five hundred reeds long, and five hundred broad, to make a separation between the sanctuary and the profane place.

NASB:

15 Now when he had finished measuring the inner house, he brought me out by the way of the gate which faced toward the east and measured it all around.
16 He measured on the east side with the measuring reed five hundred reeds by the measuring reed.
17 He measured on the north side five hundred reeds by the measuring reed.
18 On the south side he measured five hundred reeds with the measuring reed.
19 He turned to the west side and measured five hundred reeds with the measuring reed.
20 He measured it on the four sides; it had a wall all around, the length five hundred and the width five hundred, to divide between the holy and the profane.

‫טו  וְכִלָּה, אֶת-מִדּוֹת הַבַּיִת הַפְּנִימִי, וְהוֹצִיאַנִי דֶּרֶךְ הַשַּׁעַר, אֲשֶׁר פָּנָיו דֶּרֶךְ הַקָּדִים; וּמְדָדוֹ, סָבִיב סָבִיב.

‫טז  מָדַד רוּחַ הַקָּדִים, בִּקְנֵה הַמִּדָּה--חֲמֵשׁ-אמות (מֵאוֹת) קָנִים בִּקְנֵה הַמִּדָּה, סָבִיב.

‫יז  מָדַד, רוּחַ הַצָּפוֹן--חֲמֵשׁ-מֵאוֹת קָנִים בִּקְנֵה הַמִּדָּה, סָבִיב.

‫יח  אֵת רוּחַ הַדָּרוֹם, מָדָד--חֲמֵשׁ-מֵאוֹת קָנִים, בִּקְנֵה הַמִּדָּה.

‫יט  סָבַב, אֶל-רוּחַ הַיָּם; מָדַד חֲמֵשׁ-מֵאוֹת קָנִים, בִּקְנֵה הַמִּדָּה.

‫כ  לְאַרְבַּע רוּחוֹת מְדָדוֹ, חוֹמָה לוֹ סָבִיב סָבִיב--אֹרֶךְ חֲמֵשׁ מֵאוֹת, וְרֹחַב חֲמֵשׁ מֵאוֹת: לְהַבְדִּיל, בֵּין הַקֹּדֶשׁ לְחֹל.

Ezekiel left the Temple through the East Gate. The measured value of 500 reeds can in no way relate to the temple complex, because the size of the inner part of the temple complex, from wall to wall, is 520 cubits, and to this we must add the thickness of the walls, 2 x 6 = 12 cubits.

Of course, there is no way that a territory of this size could be freed from all the buildings and structures on the site of the former temples in Jerusalem. The Third Temple, in accordance with the prophecy of Ezekiel, should be built in the Judean desert (31°29'N 35°15'E), there are no buildings in that place, so we can build the Temple even now.

The dimensions of the outer wall around the estate of the Lord God are not indicated in the prophecy of Ezekiel, but we can guess about all the parameters of this wall. The inner part of the Temple, the Tabernacle, according to the prophecy of Ezekiel, has a thickness of 6 cubits, and the external building of the Temple, where the pantries are located, has a wall thickness of 5 cubits. We can use the same ratio to determine the thickness of the walls around the estate: if the thickness and height of the walls around the temple complex are set and equal to 6 cubits, then the thickness and height of 5 cubits will be appropriate for the wall around the estate.

The protrusions of the wall around the estate are necessary to fulfillment another verse: Ezekiel 45:2. According to this verse, Ezekiel's prophecy does not specify the wall thickness between the Lord’s estate, which is 500x500 reeds in size, and an external trading area of 50 cubits wide. We cannot arbitrarily alienate the land for God's possession, therefore the problem is solved simply: half of the wall sections are located on the estate, and the other half of the sections are located on the outside. Thanks to this solution, we are able to measure 500 reeds the size of the estate, and also measure 50 cubits of the width of the trading area, not paying attention to the thickness of the wall between them. Such an architectural solution is very convenient for those who trade on the square, the ledges of the wall allow each seller to have their own space, while the commercial bustle is hidden by the wall from the eye of God.

At the same time, we get 144 protrusions of the wall on each of the four sides. The protrusions themselves symbolize the mutual penetration of God's borders into the external environment, as well as the penetration of our borders into the possession of God. Low gates with sloping surfaces on the sides, as it were, call upon everyone entering this gate to humility: you enter the personal territory of the Lord God.