Trecastle's history makes it one of the longest-established Brecknockshire villages, thus the Motte & Bailey is considered an important ancient & medieval monument and the village contains a number of listed Georgian and Medieval properties.

Listed buildings in Trecastle include; 
Castle Tump (Trecastle motte and bailey), early 11th-century scheduled CADW ancient monument.

Ty Newydd Calvinistic Methodist Chapel, 18th-19th century
The Schoolhouse (now Trecastle Antiques), 19th-century Victorian Gothic schoolhouse.

Neuadd Farm (Cambridge House), dating from the 16th century.
Includes dovecote and other outbuildings.

Dan Y Coed (The Old Vicarage), early 18th century.
Includes coach house and outbuildings.

Castle House (now the Castle Coaching Inn), 19th century.

The Three Horseshoes Inn, 18th-19th century.

Pendre Smithy and Cottages, 18th-19th century.

Near the village is the site of Y Pigwn.
This consists of two overlaying Roman practice marching camps which are on the summit of Trecastle Mountain.
 They have been described as 'amongst the best-preserved and best-known Roman temporary camps in Wales.
The camps were first discovered 1849 and were planned and described by William Rees at the meeting of the Cambrian Archaeological Association at Breconin 1853.
Rees also illustrates Bronze Age burial urns which were found by a Mr Holford in nearby burial mounds.
The "Y Pigwm" camps are close to the presumed Roman road linking the Roman Forts at Llandovery and Brecon Gaer, and  a small Roman fortlet at "Waun Ddu" lies 700m to the West.
 There are standing stones and a stone circle nearby.
Trecastle's history makes it one of the longest-established Brecknockshire villages, thus the Motte & Bailey is considered an important ancient & medieval monument and the village contains a number of listed Georgian and Medieval properties.
Listed buildings in Trecastle include; 
Castle Tump (Trecastle motte and bailey), early 11th-century scheduled CADW ancient monument.
Ty Newydd Calvinistic Methodist Chapel, 18th-19th century
The Schoolhouse (now Trecastle Antiques), 19th-century Victorian Gothic schoolhouse.
Neuadd Farm (Cambridge House), dating from the 16th century. Includes dovecote and other outbuildings.
Dan Y Coed (The Old Vicarage), early 18th century. Includes coach house and outbuildings.
Castle House (now the Castle Coaching Inn), 19th century.
The Three Horseshoes Inn, 18th-19th century.
Pendre Smithy and Cottages, 18th-19th century.
Near the village is the site of Y Pigwn. This consists of two overlaying Roman practice marching camps which are on the summit of Trecastle Mountain.  They have been described as 'amongst the best-preserved and best-known Roman temporary camps in Wales. The camps were first discovered 1849 and were planned and described by William Rees at the meeting of the Cambrian Archaeological Association at Breconin 1853. Rees also illustrates Bronze Age burial urns which were found by a Mr Holford in nearby burial mounds. The "Y Pigwm" camps are close to the presumed Roman road linking the Roman Forts at Llandovery and Brecon Gaer, and  a small Roman fortlet at "Waun Ddu" lies 700m to the West.  There are standing stones and a stone circle nearby.
Trecastle