depends what you call "visiting" ;)

When I came along I just strolled around for a while. And I thoroughly went thru the Japanese garden which is kind of next to the entrance. All in all it might have took me 1,5 hours. Something like that. But I don't know if there are guided tours or so, which then might take longer.

For me it was just a nice stroll in the morning, there was not going on much yet at an early time. The atmosphere was great though.

Baerbel near Stuttgart