It was discovered on Saturday by tourists who were staying at Rolf von Andrian's bed and breakfast near Kelowna.
"They called us in a kind of emergency," said von Andrian, "They just saw a landslide."
The next day von Andrian and his wife went to see for themselves, "We saw a rock as large as a big truck I would say, about 15 feet."
The trestle that was hit is Trestle # 3 on the Kettle Valley Railway trail through Myra-Bellevue Provincial Park.
Twelve of the eighteen trestles on the trail were destroyed and then rebuilt after the Okanagan Mountain Park fire of 2003. Trestle # 3 was one of the twelve rebuilt.
"But this is the first time one has been damaged by rocks," said Ken Campbell with the Myra Canyon Trestle Restoration Society.
The entire trail, which is extremely popular with hikers and mountain bikers has been closed for safety reasons.
"Yeah it's pretty bad," said Campbell, "and not just for the tourists, but local people too who use the trail."
"The concern is that we can reconnect this link before the main season starts," said Campbell.
B.C. Parks is responsible for repairs and there's no estimate yet when that might be done.