Tried this a few years ago. We flew into Canada and decided to drive across the border to see the US side of Niagra.

With 2 kids in the car we were asked for $32 US in cash and all we had was a bunch of Canadian dollars and GBpounds so we said OK we'll just turn around but NOOOOOOOO! We had to pull over and enter the immigration building where it took nearly an hour before our passports were checked and we were questioned about trip. Then we were allowed to turn around and reenter Canada.

We did visit the US side a few years later and it's NOT as pretty as the Canadian side. So, it's worth going if you have the $$.

I have taken my German exchange students to Canada from Michigan with a visa for Canada. Here is the telephone number for a correct answer for Canadian custons: 800 622 6232

I don't know whether the number that Randy gave for Canada Customs is still valid, as they have been merged into the new Canada Border Services Agency. From the website which I mentioned in an earlier post, here are the numbers to call:

"If you have any other questions, contact the Border Information Service (BIS) line. This is a 24-hour telephone service that automatically answers all incoming calls and provides general border services information. You can access BIS free of charge throughout Canada by calling
1-800-461-9999. If you are calling from outside Canada, you can access BIS by calling 204-983-3500 or 506-636-5064 (long-distance charges will apply). If you call during regular business hours (8:00 a.m. to 4:00 p.m. local time, Monday to Friday, except holidays), you can speak directly to an agent by pressing "0" at any time.

You can also visit our Web site at www.cbsa.gc.ca."