I do a ~25 minute walk basically every day -- the key for me is doing a defined loop. Doesn't matter where, just so long as it's a single loop (eg no repeating, no backtracking) and it always stays interesting for me. And in fact the more you do it, the more it becomes rote, and the LESS you care about the route being interesting. You can just tune out, go on autopilot, and keep thinking about what ever you want to keep thinking about but also get some exercise in.

Just my $0.02