I just thought of a graphical idea: Why not use bridges for river crossings? It could be a simple tile that changes per era.
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"Wait a minute..this isn''t FAUX dive, it's just a DIVE!"
"...Mangy dog staggering about, looking vainly for a place to die."
"sauna stories? There are no 'sauna stories'.. I mean.. sauna is sauna. You do by the laws of sauna." -P.