This is not true of course. Such anomalies can only be detected with sensitive equipment and cannot account for these places. There are several things which enable us to sense which way is up. The balance mechanism in our inner ears is one system we have, but visual clues are also important and can be overriding. If the horizon cannot be seen or is not level then we may be fooled by objects which we expect to be vertical but which aren't.
People often overestimate the angle of a slope.
If you are standing on a slope of 5 degrees it may seem like you are on a slope of 30 degrees. Because of this effect the anti-gravity illusion can seem stronger than it should be even when you know the cause. A search on the web turned up a surprising number of examples of this illusion. Most are natural while others have been constructed in theme parks. Here is an incomplete list for those who want to find one.