A grand tomb or building housing a tomb, often for a ruler or important figure.
This mausoleum was built for an ancient king.
Specifically a Shinto shrine; the term is somewhat formal or literary.
There is an old Shinto shrine at the foot of the mountain.
Compound of 廟 (mausoleum/shrine) and 宇 (building). The exact historical derivation is uncertain, but the kanji combination is conventionally associated with grand religious or funerary structures.