Sites in Hatfield and Gorhambury near St Albans have been added to Historic England's list of protected sites.
The houses in Old Hatfield, and the Pondyards, join over 400 other locations added to the National Heritage List for England during 2020, released on December 16.
Old Hatfield's 1, 3 and 5 Park Street, near the Eight Bells and the Horse and Groom, had many uses over the years. It is most likely to have started as an inn in the mid-17th century, before it became a home, followed by shops and most recently offices in the late 20th century.
The surviving historic fabric of the building has square panelling and a late 17th century oak staircase, along with the very rare survival of two 17th century wall paintings, according to Historic England, which have recently been unveiled.
The murals, which portray grotesques and a pattern that imitates a cloth-like texture, are in excellent condition and seem of particularly high quality for a building of this.
The discovery has meant the buildings have gone from Grade-II to II* listed buildings.
The Pondyards at Gorhambury, a series of water gardens created in 1608 for Sir Francis Bacon, the English philosopher and statesman who counselled Queen Elizabeth I and King James I has also been protected.
These water features, which were designed to display aquatic plants or ornamental fish, were extremely popular among the courtiers of Renaissance England, Historic England explains, and were developed as a landscape artform.
The foundations of the Pondyards are in good condition and it is thought that archaeological items may still survive within the banks and base of the ponds.
The Pondyards, part of Bacon’s Hertfordshire estate, origins, history and influence on future landscaping is helped by surviving historic documentation such as drawings, written descriptions and Bacon’s own essay about garden design.
Duncan Wilson, chief executive of Historic England said: "Despite the challenges that the heritage sector has faced this year, 2020 has seen many brilliant additions to the List.
"From a picturesque footbridge in Essex to an excellently preserved Victorian railway station café in the Midlands, we want to ensure England’s rich and varied cultural heritage is protected so that the public can continue to cherish the heritage that makes their local places so important."
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