These are examples of strongholds that have been built, or are planned, for my Stolen Lands game.
Midmarch – is a whole province that contains a number of different individual strongholds, bound together by The Governors Lands.
Narlemarch Reserve – A pure wilderness estate, composed of half-a-dozen hexes, established by rangers and druids to protect a group of Fey. Only the most basic of developments are allowed and it is regularly patrolled by scouts. You could, of course, build a much larger wilderness estate.
Midmarch Rural – The Governor’s estates, with villages, farms and other country businesses. It is the glue that connects the other strongholds together.
Tusk – an independent city, managed by a group of PCs. It is the Provincial Capital and regional trade centre - many PCs have their main businesses there.
Ringbridge – a small town run by a PC Lord, tasked with guarding a strategically important river crossing. It is heavily defended, and once the Town is ‘finished’ the local Lord will most likely develop other business interests.
leMaistre Estates - Henry leMaistre runs a successful merchant house (among other things) and the income from that is going towards building his personal stronghold. The long term plan is to ‘own’ a number of small towns and villages spread around Midmarch (and perhaps beyond), rather than one large holding.
Canals – a stronghold underdevelopment, plans to hold two contiguous hexes, based around a canal that bypasses waterfalls and cascades.
Tatzleford – is under development, but it is planned to be a town in the middle of a forest, surrounded by managed-wilderness hexes. It may, eventually, meet up with the Narlemarch Reserve to the north and create a 'national park' like area.
Southmarch – A proposed offshoot that will be completely independent and have its own Ruler/Governor/Lord. The main protagonist is currently building a business that can finance the development – and networking with other PCs to gain their support. I suspect it could finish up as an independent City State.
Others – I suspect that other PCs will latch onto Southmarch and form their own associated Strongholds.
Those are some examples - but there are many other possibilities. Don’t be afraid to work with other people, from the examples above; Tusk, only developed into a city because a number of Characters worked together. Tatzleford (Driven by Erastil’s philosophies) and the Midmarch Reserve (Driven by Green Faith philosophies) make for a larger protected area than either could manage alone. If someone else comes along and claims a few hexes to the south – that would make quite a significant wilderness in the middle of developed lands.