Introduction and request for advice

[Calendril]

Hello all - I'm brand new here but with a problem I've been trying to solve for the better part of a year. I'd be very grateful for any advice.

I'm trying to put together a fantasy map. I've got the outline of the major continent and I can do the artwork, but I'm hoping to find advice on geography. By that I mean I want it to have realistic features in a realistic combination that lead to believable trade routes, city placement, agriculture, etc.

It may not be all that critical, but I've held off setting up the major cities and all because I feel that the geography should be fundamental to the concept.

The dark purple area in my map has to be kept isolated from the central area - I figure I'll put "sea monsters" in the middle to prevent quick travel north and south. The only features I know have to be there are Swiss Alp style mountains to the east and a harsh desert to the west.

So - after that wordy introduction, I'm looking for guides or advice on how to place logical geography and how to extrapolate civilization growth based on that.

Again, any help at all is deeply appreciated!

-Cal