Gyldén is the remnant of a lunar

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 that is located to the northeast of the walled plain Ptolemaeus

Ptolemaeus (lunar crater)

Ptolemaeus is an ancient lunar impact crater close to the center of the near side. To the south-southeast Ptolemaeus is joined to the rim of the crater Alphonsus by a section of rugged, irregular terrain, and these form a prominent chain with Arzachel to the south...

 on the Moon. It lies along the prime meridian

Prime Meridian

The Prime Meridian is the meridian at which the longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.An international...

 of the selenographic coordinate system, and less than 150 km south of the lunar equator

Equator

An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

. Nearby craters of note include Herschel

Herschel (lunar crater)

Herschel is a lunar impact crater located just to the north of the walled plain Ptolemaeus. Just to the north is the flooded crater Spörer, and due east lies the disintegrated crater Gyldén...

 to the west, the flooded Réaumur

Réaumur (crater)

Réaumur is the remains of a lunar crater located on the southern edge of Sinus Medii. It lies to the northwest of the large walled plain Hipparchus, and east of Flammarion. To the south is Gyldén, and farther to the south-southwest is Ptolemaeus....

 to the north, and Hipparchus

Hipparchus (lunar crater)

Hipparchus is the degraded remnant of a lunar crater. It is located to the southeast of Sinus Medii, near the center of the visible Moon. To the south is the prominent crater Albategnius, and to the southwest lies Ptolemaeus, a feature of comparable dimensions to Hipparchus. Horrocks lies entirely...

 to the east.

The heart-shaped rim of this crater is in poor condition, having been eroded by impacts until the disintegrating remnants form an uneven ring of peaks and valleys around the interior floor. The satellite crater Réaumur A is attached to the northern rim. A wide cleft cuts through the western rim, continuing to the north-northwest past Spörer

Spörer (crater)

Spörer is a lunar crater that lies just to the north of the crater Herschel, and southeast of the lava-flooded Flammarion. To the southeast is Gyldén, and to the northeast is Réaumur....

. The interior floor is relatively featureless, although the small crater Gyldén K is located just to the southeast of the mid-point.

Satellite craters

By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Gyldén.

Gyldén	Latitude	Longitude	Diameter
C	5.8° S	1.0° E	6 km
K	5.5° S	0.6° E	5 km