Today Poros consists of two islands: Spheria, which is the modern town of Poros, and Kalaureia, the larger and less populated island. The archaeological site of Kalaureia lies on the island with the same name c. 6 km from Poros town, and can be approached by a winding road either from the town or from the village of Askeli on Kalaureia. The site is on a plateau between the hills of Aghios Elias and Vigla and has a commanding position c. 200 m above the sea level. To the north there is a visual connection with the peninsula of Methana and the islands of Angistri and Aigina, and to the south it is possible to catch glimpses of the sea against the background of the steep Peloponnesian coast. Beyond Aigina, Pireus and the coastline of Attica are visible on clear days.
Our investigations show that the plateau is partly manmade as it was created over time by generations of terraces built in order to extend the area of the sanctuary when need arose. What the terrain looked like originally is still only partially known. A telling detail is that the Early Iron Age remains were at places found underneath more than 1 m of terrace fill from later periods. The terrain in and around the sanctuary obviously underwent a profound change from the Archaic times and onwards. In more recent times, the excavation in 1894 left its marks in the landscape. Some dumps of excavated soil, now eroded to low mounds, are still visible on the site, particularly inside Building A and to the south of it. Some time after the excavation a farmstead was built on top of some of the buildings in the western part of the sanctuary thus causing further damage especially to Building F, the remains of which were practically obliterated in the process.
The road that crosses the site was built in 1971 cutting off Building G from the remainder of the structures excavated in 1894. In 1978 the site was expropriated by the Greek Archaeological Service, and the area to the north of the road was fenced in. The fenced-in area was extended towards the east in 2006, but the true extent of the sanctuary is still unknown. The archaeological site, however, extends far beyond its borders. To the south of the sanctuary and to the south of the modern road are the remains of the ancient city of Kalaureia. There is a dense scatter of surface artifacts in the whole area and stretches of walls can also be seen. Remains of a city wall are still standing some distance to the southeast of the entrance to the archaeological site. A geophysical survey, conducted in the area in 2006, indicated sub-surface town houses with built-in cisterns or wells.
To the north of the sanctuary the terrain slopes steeply towards the bay of Vayionia, where Samuel Wide in his report of the 1894 excavations mentions ancient shipsheds (boathouses). The sheltered western side of the bay could certainly have served as the port of the ancient Kalaureia, but there are other possible port locations as well. Wide also mentions tombs both to the west and to the east of the sanctuary but those cannot be located today.
Most of the island of Kalaureia is today covered by a dense forest of pine. Shrubs grow on steep slopes while occasional olive grooves can be found on sheltered locations. Wine is still cultivated on the plain of Foussa to the northwest of the archaeological site. Analyses of charcoal from the excavations since 2003 reflect what was used as firewood in the sanctuary and they reveal that the pine forest did not exist in antiquity. According to Maria Ntinou, the majority of all charcoal originates from olive trees, which suggests the existence of substantial olive grooves in the vicinity of the sanctuary. Other, more sun-demanding species, such as carob, indicate clearances, which may mean that animals were also herded nearby. Pine is almost entirely absent from the samples. An archaeobotanical study, conducted by Anaya Sarpaki, showed the existence of olive, grape, and herbs with medicinal use, which are still extant in the flora of Poros.
The bedrock in the sanctuary area is of a soft, yellowish limestone, with occasional outcroppings of harder, greyish limestone. Both were used as building materials in the sanctuary. Stone quarries have been located to the north of the sanctuary towards the Vayionia bay, and to the south along a footpath to the village of Askeli.