Fort Vastenburg, Dutch fort in Kedung Lumbu, Surakarta, Indonesia

Fort Vastenburg is a square Dutch fort with four corner bastions, a six-metre-high bearing wall and a dry moat, entered through portals on the west, east and north sides. Its interior buildings, including officers' quarters, a military hospital and a drugstore, were demolished; only the walls and the open central courtyard remain. The western main portal once had a bascule bridge, now gone.

The Dutch East Indies Company built the fort between 1743 and 1745 as a strategic trading position under Governor Baron van Imhoff. It later became a central administrative hub and played a key role in Dutch control over the Javanese region.

The fort served as the seat of Dutch authority in the region and shaped Surakarta's urban landscape with European architectural standards. Visitors can still observe this colonial presence through the building layouts and structures that follow military design principles.

The interior buildings and barracks were levelled, so the site is now an open grassy field enclosed by the 6-metre wall and dry moat; only the east, west and north portals remain. The western drawbridge is gone. Ground is uneven in places, and the field is used for events such as the Solo City Jazz Festival.

The name on the parapet, "VASTENBURG", is paired with the dates "1745-1975". Dutch sources place construction in 1755-1779 and repairs in 1832, while English sources credit Frans Haak with a start in 1746 and completion in 1765; early records call the fort Grootmoedigheid.