Because of the requirements of commerce, where it's at on the river and so forth.
From the time.com
You continue to cross back and forth across the river to get to other areas of the city.
From the gothamgal.com
Ambulances raced back and forth between the river and the hospitals for several hours after the stampede.
From the chron.com
If the lock is closed, none of those boats can go back and forth between the river and lake as they do now.
From the suntimes.com
Sipping my sprightly white wine, I gazed at the tiny two-car ferry sliding on its cable back and forth across the river.
From the kansas.com
Christmas morning spilled forth a river of tiny gifts, each wrapped as I knew only one person to do, meticulously, in paper richer than any my grandparents would use.
From the post-gazette.com
Then they turned up into the river, because they dared not sail forth past the river for hostility, because the land was all settled on the other side of the river.
From the en.wikipedia.org
Still overcome by emotion, Imai paces back and forth along the Sunaoshi river that runs through his small hometown of Tagajo, his knee-high wading boots scraping along the ground.
From the denverpost.com
That seems a little far for a day trip, but it can of course be easily broken into sections and you can switch back and forth across the river as attractions take your fancy.