The Newborough mausoleum is a circular stone building, measuring 60 ft. diameter with 15 ft. thick walls. It has 2 floors and barrel vaults. It is situated on a wooded rise in the south-eastern part of the park (Glynllifon Park - NPRN 86377), about a kilometer from the house (NPRN 26526). Work on the mausoleum was begun by the 2nd Lord Newborough in 1826 and was unfinished at his death in 1832. The 3rd Lord Newborough continued the work, but stopped when it became necessary to divert funds to the rebuilding of the house. The planned 2nd floor chapel was never built, and the building was never used as a mausoleum.

(source: text attached to NPRN 86377)