I'll add a (c) to Gidde's 7 (a) & (b) points - also, moist air as it rises - like approaching a mountain range and getting pushed up and over - tends to cool. Cooler air can't hold as much humidity, so some falls out as rain. Thus the upwind side of ranges tend to be wetter, and the downwind sides tend to be drier - what's called a "rain shadow". If your prevailing winds are from mostly the same direction year-round, then maybe the downwind side is outright desert. If the wind patterns shift during a year, then you just get different drier and wetter seasons. If said mountains are getting their moisture in winter, and it's cold enough to snow, then that snow melting months later may even out the stream flow, even if the summer pattern for the snowy area is drier.

The main reason you get the impression rivers spring from mountains is that water DOES flow from higher ground to lower. So if there IS any high ground, that's no doubt where *some* streams start. But in a flat-ish bit of territory, the bit of plains that's ten feet higher than others will be a source. A cool side effect of this is that you can imply even slight elevation distinctions just by your river network.

A possible solution for your #6 could come from an amplification of your #3. To wit: just how extensive are these two continents? If the area you're focused on is in *just* the right latitude with the right topography you could get a whole bunch of clouded days. Too, high-altitude haze could obscure a clear view of sun and stars, even when lower-level clouds part. Say, the 'natural' temperature of your planet was chilly, and a period of increased volcanism (per Gidde's #4) is currently spewing a fair bit of greenhouse gases -- you might be in a geologically-brief period of artificial warmth, with atypically high cloud cover. Too, whether cloud cover blocks sunlight (for the aforementioned chill effect) or retains heat (for the currently-feared earthly greenhouse effect) is a matter of the kind of clouds, altitude, and global coverage. I can imagine situations where certain latitudes got 'too many' clouds, with the balance of the globe getting random weather patterns and plenty of sun to keep the seas warmed. A largely-water-covered world will have climate that's moderated mostly by the oceans, even if the land gets weather that would push things to extremes. So again - how big and where are these two landmasses? And do you mind the islanders having a different view of the sky (clearer) than the continental folk?

For that matter, do you need the entirety of both continents to be habitable? A bit of imagineering with climate and weather patterns could probably get *some* of each near-perpetually cloudy, even if other parts have this mythical "full sunshine" thing going on. There's parts of Earth without good aerial photography precisely because they have clouds so much of the time.



Hmmm - for your #2, town spacing, I'd want to know if these continent-spanning nations have been unified a long time, or if there was a heritage of smaller political units? Reason being, artificial boundaries like political borders can disrupt otherwise logical locations. Say, a fertile plain might 'logically' support one really big market / gathering city, but if there were antagonistic or even just competing nations dividing the area, *each* might have its own big city. Even simple geological separation could do that - opposite sides of an unbridgeable river might have separate big cities just a mile apart.

A further deciding condition is what historical level is your land's development? If travel is all afoot or by rowboat, settlements will generally be smaller and closer than if one has railroads and steamships.

While human habitation demands water, we're a cantankerous species, and significant urban areas DO happen in inhospitable areas. One just has to have a reason for them to be there - doesn't have to be explained in your story lines, you just have to have some idea - because those hidden reasons will have visible consequences for society. Rich mines? Religious significance? Tourism? Trade route across inhospitable areas? Too much water can make things just as dicey for urban accumulation as too little - bayous, swamps, and deltas tend to be sparsely settled.

Don't be daunted by all this worldbuilding - be elated! You can build soooo much richness into a setting this way, when less energetic or less spiral-shaped minds :-) make do with vague idealized medieval western-European countryside. To be fair, some of those authors just need a middling-believable setting for interaction between characters whose nature or plot doesn't demand any detail of setting. Not me. I NEED the setting to spawn the characters and situations. I let a world grow, and situations arise, THEN I decide what likely would happen.

Back on #7 - you can get some landforms by fault-block shifting. Picture a levelish area, with two cracks parallel. Drop the middle bit a few hundred feet, and you can have some dandy cliffs around a valley. Push the middle bit up, which geological processes can do, and you can get a big raised plateau. If it's big enough to gather lots of rainfall, then rivers leaving it could have spectacular waterfalls. Dandy places for waterpowered mills too, by the way. Some continents have raised areas inland with coastal plains, and a significant escarpment between - much of the eastern seabord of the US is like that.

Btw I heartily approve of the avatar. Have fun with the worldbuilding!