523 West 135th Street is a five‑story, 1910 pre‑war rental building with 20–21 units, a mix of free-market and rent-stabilized apartments. The building offers an on-site superintendent and voice‑intercom access. Most units have been recently renovated with hardwood floors, modern kitchens featuring stainless appliances and dishwashers, and some include in-unit washer/dryers.