Headed for auction soon near The Woodlands: this 7,000-square-foot mansion sits on a private island surrounded by a moat-like ring of water in Magnolia. Take a look inside.

Designed for owners of $5 million to $20 million properties, the private club operates across prime destinations with memberships priced at $100,000.

Mouse Island, a seven-acre island with a rocky shoreline and mature woodlands, is for sale for $5 million and was once owned ...