proto-Indo-European geography.

It seems to me that the myth of the Pripet Marshes has never been properly debunked. The headwaters of the Vistula are on the northern slopes of the Western Carpathians, about 250 mi from where the real-world Pripet Marshes may ever have extended even in prehistorical times (so, incidentally, are the headwaters of the Volga and the Dniester, but the confluence of the Pripyat' and the Dnieper, approximately the site of the Chernobyl disaster, lies well within the primaeval swamp area).

You've debunked it for me. But the image of the vast eastern swamp, stomping ground of the last aurochsen in Europe, is still with us. This is exactly the kind of information I've been looking for.

As you set out from the upper Vistula towards the Marshes, you pass through the Vistula/San 'mesopotamia', a fertile plain with loess soils in which the neolithic farmers of the Linear Pottery culture took a lively interest as soon as the colonisation of Northern Europe had begun. Farther to the northeast lies a range of hills called Roztocze; behind them, the moderate Lublin Upland, also with a reputation for good soils and a record of neolithic farming (Lengyel culture sites). Then you walk down from the hills into the valley of the River Bug (the largest tributary of the middle Vistula), and it is there that the swamps really begin. The Pripyat' is a stone's throw on the other side of the Bug, across the divide between the Baltic and the Black Sea basins.

I see. From what I've read, it's the Bug that seems to be the important river for access into Hungary.  I forget the exact reference, but the Bug valley also seems to be important as the interchange area for Danubian to Pontic trade relations (where Sredny Stog got it's metal). You see the Prut and wonder about it -- but are told it's not really a viable entry; swamps!

The important point is that between the Pripyat' system and the Carpathians there's plenty of space for travelling; and the watershed between the San (Baltic) and the Dniester (Pontic) can be crossed by a child, not to mention grown-up shepherds or farmers and their livestock.

This is the important point.  It really is. I'm looking for the plausible trade, migration and even 'invasion' routes of late eneolithic / early Bronze Age northern Europe.

The Moravian Gate [....] The name derives from the Czech province of Moravia, not directly from the River Morava, which flows more to the south. The gap was actually created part by the upper Oder, part by the Beczva (a tributary of the Morava).

More stuff I've never really heard of. As I said, no one teaches you these things. You don't even get it in college-level courses. I knew of Moravia and Bohemia and both of the Morava Rivers (why the doublet?). Anyway. We are speaking of a gap in the Carpathians that lets you into, oh, I guess this would be Silesia,  and thence to the North European Plain.

It all depends on your chronology. If you mean Bronze Age Proto-Germani or Proto-Balto-Slavs, I'd say it's highly unlikely that they lived in splendid isolation. The first really indigenous neolithic culture of Northern Europe, the Funnel Beakers, already covered much of the region, including almost all of modern Poland. The same is true of the later Globular Amphorae; and the Corded Ware complex extended from the Volga to Scandinavia and the Rhine. This testifies to the existence of trading networks and lively contacts even before the advent of the bronze axe. The Bell Beakers of the Bronze Age are found from Iberia to the Ukraine.

I'm aware of these 'names'. I'm still putting it all together. The 'Corded-Ware Horizon' seems to be the current buzz-word.

The languages of Northern Europe (Germanic, Baltic and Slavic) share a lot of vocabulary and display other similarities which are apparently due to areal convergence.

Here, I think we part, mostly because you're contradicting what I've read.

[...] That's why I prefer deeper chronologies, even at the cost of sacrificing the Pontic homeland. As a linguist, I'd feel more comfortable with dates like 6000-5000 BC for PIE (ancestral also to Anatolian, of course), so that the linguistic evolution of the family could be traced as a series of gradual splits, slow dispersals and secondary convergences rather than a single Big Bang. This is also why I find the theory that the Linear Pottery folk were already IE pretty attractive.

How do you speak to Andrew Sherrat's 'Secondary Products Revolution' and the supposed impossibility of the words associated with it being borrowed by IE languages without showing evidence of their status as loan words? From what I've read so far, I seems it was the knowledge of how to build sturdy carts and wagons, along with the necessary knowledge of livestock raising and how to put oxen to the yoke, that propelled the IEs in a Big Bang (horseback riding was a very useful and perhaps crucial adjunct). In the case of grasslands, this was an empty ecological niche -- and their ability to fill it was limited only by their and their cattle's ability to reproduce. Once you get into the Northern European forest, however, other conditions ruled. You had different economies.

But I'm getting off the main thread here. I've looked here and there for a decent introduction to East European geography. There is none! What you get from maps is not entirely satisfactory; for Germany or the United Kingdom, it's easy to find very large scale maps; for Eastern Europe, you often have to make do with continental-scale maps. I have never seen a really detailed set of maps for the former Soviet Union. It's like trying to make sense of the hydrology of the Mississippi basin by looking at a map of North America.

My understanding of what the steppe looks like, and my speculation on what forest-steppe is were not far from the mark. Still, you need to be assured you're not stumbling around in the dark making inappropriate guesses.

Agriculturalists build their roads along the river valleys. Pastoralists have trails that connect adjacent river valleys. It's the latter I'm primarily interested in. It's the Ural to the Samara-Volga, then the Volga to the Don-Donets, then to Dneiper, then across to the Dneister, etc. These are rivers whose names I know, and who's length's I can trace on a map, but as to how you get from east to west or west to east, I don't know. Could there possibly be something we could call 'the Indo-European Road' (i.e., the western extension of the Silk Road, leading towards Hungary or the Vistula.