The ruined Hartwell church was designed by the architect Henry Keene and completed in 1756. It is one of the most important early Gothic revival churches in England and is Grade II* listed. It has an octagonal centre with twin towers. In the north and south bays are rose windows, other windows are represented as ogee arches. In the clerestory are quatrefoil windows. Inside, the church once had a plaster fan vault but this has now fallen in, and the church's windows are boarded. Today the building appears more as a garden folly, than a former place of worship.
Attached to the estate is the former hamlet of Lower Hartwell.
Hartwell House in the village is a grade I listed building in a 90-acre park, part of the Hartwell Estate owned by the Ernest Cook Trust. The house was once the residence of the exiled future king of France Louis XVIII. Since 2008 it has been leased to The National Trust and is run as a hotel by an independent company, Historic House Hotels Ltd.
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- Hartwell and the Ernest Cook Trust
- Hartwell House
- William Henry Smyth, Ædes Hartwellianæ: Or, Notices of the Manor and Mansion of Hartwell (1851)
- William Henry Smyth, Addenda to the Ædes Hartwellianæ (1864)