Question: What is the land area of this country where the largest Roman city gate north of the Alps is located ?

text: List of oldest known surviving buildings
By country
The following are among the oldest buildings in their respective countries .
This article lists the oldest known surviving free-standing buildings constructed in the world, including on each of the continents and within each country. Building is defined as any human-made structure used or interface for supporting or sheltering any use or continuous occupancy. In order to qualify for this list a structure must:
Building Country Continent First Built Use Notes
Weibbe Hayes Stone Fort Australia Australia 1629 AD Stone Fort Old stone fort built by the survivors of the Batavia shipwreck
Tomb of Seuthes III Bulgaria Europe 450-400 BC Tomb The tomb was originally a monumental temple at Golyama Kosmatka Mound , built in the second half of the 5th century BC . After extended use as a temple , at the later part of the 3rd century BC the Thracian king Seuthes III was buried inside
L'Anse aux Meadows Canada North America c. 1000 AD Settlement Located on the northernmost tip of the island of Newfoundland , the Norse settlement is widely accepted as evidence of pre-Columbian trans-oceanic contact
Hulbjerg Jættestue Denmark Europe 3000 BC Passage grave The Hulbjerg passage grave is concealed by a round barrow on the southern tip of the island of Langeland . One of the skulls found there showed traces of the world 's earliest dentistry work
West Kennet Long Barrow England Europe 3650 BC Tomb Located near Silbury Hill and Avebury stone circle
Yeha Temple Ethiopia Africa 500 BC Temple Oldest standing structure in Ethiopia
Barnenez France Europe 4850 BC Passage grave Located in northern Finistère and partially restored . The structure is 72 m long , 25 m wide and over 8 m high . The oldest known building in Eurasia
Porta Nigra Germany Europe 180 AD Roman city gate It is today the largest Roman city gate north of the Alps
Knossos Greece Europe 2000-1300 BC Palace Minoan structure on a Neolithic site
Dholavira India Asia 2600-2100 BC Reservoir A planned urban settlement comprising reservoirs , pottery artifacts , seals , ornaments , vessels , etc
Chogha Zanbil Iran Asia 1250 BC Temple One of the few extant ziggurats outside of Mesopotamia
The Ziggurat of Dur-Kurigalzu Iraq Asia 14th century BC Probably religious rituals Built by the Kassite King Kurigalzu I
Newgrange Ireland Europe 3200-2900 BC Burial Partially reconstructed around original passage grave
Monte d'Accoddi Italy ( Sardinia ) Europe 4000-3600 BC Possibly an open-air temple , a ziggurat , or a step pyramid , mastaba A trapezoidal platform on an artificial mound , reached by a sloped causeway
Ġgantija Malta Europe 3700 BC Temple Two structures on the island of Gozo . The second was built four centuries after the oldest
Cuicuilco Circular Pyramid Mexico North America 800-600 BC Ceremonial center One of the oldest standing structures of the Mesoamerican cultures
Mission House New Zealand  1822 AD Religious Built by Māori and missionary carpenters
Mehrgarh Pakistan Asia c. 2600 BC Mud brick storage structures A complex of ruins with varying dates near Bolan Pass
Sechin Bajo Peru South America 3500 BC Plaza The oldest known building in the Americas
Dolmens of North Caucasus Russia Europe 3000 BC Tomb There are numerous tombs , some perhaps originating in the Maikop culture , in the North Caucasus