The fictional Prospect Garden in the classic novel 红楼梦 hóng​lóu​mèng, built for Jia Yuanchun's visit home

A magnificent place, or a location that is strikingly new and complex to a visitor, often used in reference to the idiom 刘姥姥进大观园 liú​lǎo​lao​jìn​dà​guān​yuán