This looks like another fun challenge, and I have a(n old and rather neglected) world in need of a colony town.

Supplementary Information:
Kessila sits just west of a mountain range and a good distance east of an ocean-connected sea. The sea region was briefly home to a large empire, but internal politics eventually caused the empire to fracture. In the early days of the empire a Wall was established to guard the main pass which nomadic raiders used to cross the eastern mountain range and prey on the outskirts of the empire. During the generations of warring after the empire's collapse the raiders finally breached the defenses and destroyed many of the towns nearest the Wall.
After the warring ended three powerful states emerged, and working together they repaired and extended the Wall. New colonial settlements were established along the Wall to provide strategic reinforcement, expand the influence of the states and help with burgeoning populations. By this time the tech level of this part of the world looks something similar to Ancient Greeks/Romans. In Kessila we will hopefully see that influence in the ordered approach to the layout.
Although there will be six or seven cities established along the Wall during this time, the thing that sets Kessila apart (and what qualifies it as an entry for a 'colonies' challenge) is that it is not just one settlement, but three, with two of the major powers and a religious cult all showing interest in settling the location.
Kessila is built over one of the razed towns, which was itself built on an older sanctuary. Kessila is in a drier region, so I originally wanted it supplied by a Qanat-style water system emerging from a cliff face. Although the Qanat idea may not be used, the idea lead me to (4th century bc) Priene, which I thought had unique features inspiring some character in what could be an otherwise very ordered and orthogonal town layout. I will try to let Priene inspire me despite Kessila being nowhere near a large body of water. I feel like the topo will be an important element, so I will spend some time laying that out here at the beginning, and maybe continue to refine it as I go along. The topo will definitely have to feature in the final layout, but I am not sure yet how much or what detail should be seen in the town itself.

Haverfield (in Ancient Town Planning) give us some numbers for streets/blocks in Priene, so we have something to work with concerning scale.

...and some eighty blocks of private houses, each block measuring on an average 40 x 50 yds. and containing four or five houses. The broader streets, rarely more that 23 ft. wide, ran level along the terraces and parallel to one another. Other narrower streets, generally about 10 ft. wide, ran at right angles up the slopes, with steps like those of the older Scarborough or of Assisi...
Priene - Wikipedia, the free encyclopedia

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There is not much to look at yet, just a first draft of the topo. The center of the map is an oversized hill, and the top of it will eventually be walled off as a sort of fort/acropolis. Below that is a square roughly the size of Priene sitting on a plateau. I already want to redo some parts of the topo, but the next step will getting Kessila's areas walled off and doing a rough layout of the streets. I am not sure how much of this will be visible in the final layout, I may end up cropping out the acropolis area to focus more on the town itself.