In the footsteps of Pilis reforestation

• From the Klotildliget railway station we follow the P+ marking to the junction near the Iluska spring.
• At the intersection we turn right onto the P trail, pass the Iluska spring, and climb to the ridge of Fehér-hegy.
• We turn left onto the ST marked nature trail into the Zajnát Mountains forest.
• We pass the Sas rock, then descend on the ST trail to the gas pipeline corridor.
• We walk left on the S trail into Pilisvörösvár.
• At the first junction we turn left onto the S+ trail, which leads to the Szabadságliget railway stop.

Detailed description of the hike:

Klotildliget, oak grove, pine garden

Klotildliget got its current name in the 19th century, reflecting two historical moments: the grove originates from the “Boldogliget” used by the Romans, and Klotild was the wife of Archduke József. After the railway opened in 1895, enabling urban development, the archduke parceled out his estate near the tracks in the late 19th century, where villas sprang up. Initially mostly Budapest officials, later military leaders due to nearby barracks, moved here, making the area suspicious during the communist regime in the 1950s. After the war, many Germans and Slovaks were displaced here, replaced by Hungarians from Upper Hungary and later by people labeled as class enemies from Budapest. We start walking along the P+ trail through Klotildliget’s charming streets lined with gardens and tree rows, soon reaching the forest edge. The trail turns right here and slowly reaches the town edge, where we turn left into the woods.

The path gently but constantly climbs through the oak forest on the hillside. In the early 20th century, this area was mostly barren – as the name of the Great Bare Peak (Nagy-Kopasz), whose lookout was demolished in 2025, suggests. The building modeled on a bell tower was named after Antal Dévényi, to whom the area owes its forest cover today. He was born into a forestry-hunting family and often roamed the area with Archduke József. He served as forester and master hunter in the Piliscsaba grove. Reforestation of cleared mountains in the 18th and 19th centuries was pioneering work; he was buried in his hometown Piliscsaba in 1994.

In the 18th-19th centuries, industrial-scale logging for the growing needs of Budapest left enormous clearings, scrub and shrub areas, and in other places, the freed slopes were used as pastures. Wind-blown sand and muddy flash floods threatened the villages nearby on bare hillsides. The expanding interest in hiking and constant wood demand made reforestation necessary. Where soil washed away less due to terrain, native species were planted by hand, while other zones started reforestation with pine. (We are not far from the former nursery garden.) Soon we will encounter ingenious solutions and stations of the sophisticated reforestation work.

After crossing a low ridge and a gentle descent, another intersection appears, from where we follow the P marking right – difficult to discern amidst the dense signs. Shortly we reach the area's only major water source, the Iluska spring. Unfortunately, it is dry most of the year, but it's worth sitting on the benches to rest before the climb up Fehér-hegy. (The spring is named after Iluska, who washed in the Sándor Petőfi creek.)

The black newcomer

We leave the resting place along the P trail. To the left of the wide dozer road, the forest landscape changes: pines mix with deciduous species (mainly Turkey oak), which reflects a stage of reforestation efforts started here in the mid-20th century. Antal Dévényi and his team, who began afforesting the barrens, originally planned that after black pines contributed to humus formation and prepared the soil for native species, deciduous forest planting could begin. Thus, vegetation similar to the original may develop here, or – as here – a grove with pines only as a coloring element. This is close to the natural habitat of black pine, which grows in groves and mixes with deciduous trees, resulting in a rich shrub and herb layer.

At a fork, we turn left, then shortly right on a barely noticeable, scrub-covered path. The path leads along a clearing fence; from above, the Pilis-tető block is visible. We climb steeply to the ridge, cross the top of Fehér-hegy (though we avoid the summit), and now we walk along the edge of the pine kingdom. We don't stay high for long; soon we turn left onto the nature trail marked ST. This begins the most pleasant section of our hike: we enter the black pine realm of the Zajnát Mountains, characterized by steep slopes, prominent rocky towers, and white barren spots. The air is scented with resin, and further ahead only black pines cover the hillside.

The path winds with sharp and gentler bends along the hillside, first with narrow ledges gently furrowing the slope, then we see stakes and planks along the edge, showing the superhuman engineering needed to reforest the mountain. When the dense forest disappeared from the Zajnát Mountains by the early 19th century, the grazed animals partly ate the grass and helped loosen the soil by trampling. Rainwater freely drained away, creating deepening gullies that eventually washed down to the dolomite rock within half a century. Besides, the dolomite rock, prone to graveling, did not help vegetation regain ground quickly, as it weathers very slowly, making soil formation especially slow. The nearby railway tunnel and the Kopár inn sitting in the pass hint at a landscape mostly turned into dry rocky ridges.

Shrubs were not completely safe, either, as the alien mouflon, introduced by Archduke József from Corsica for hunting, was present in the Pilis. Interestingly, when extinct from its original home, four pairs of animals were taken from the nearby Buda Hills to an island to repopulate their natural habitat.

The covered mountains

After several failed attempts, afforestation of the barren areas finally succeeded on Őr-hegy near Vörösvár in the 1920s. After WWII, under Antal Dévényi’s leadership, reforestation around Piliscsaba began. Initially, covering the almost barren, partly rocky areas with sufficiently thick soil was essential. Entire hillsides were terraced to sow seeds on narrow shelves. The planted species was black pine, specialist on exposed limestone cliffs, Mediterranean in origin, tolerant of drought and loving sunshine, also liking calcareous soil. For soil protection and shading, terraces facing the slope were often bordered with woven brushwood and in recent decades with stake-fixed boards to protect fallen leaves and branches from the wind and erosion. Furrows were cut in terrace centers where locally collected cones scattered seeds. Needle and branch fall of growing pines increased the humus soil layers.

The original plan to thin black pines over time and mix native deciduous species was overruled by state policies seeking quick profits from fast-growing conifers. But black pine wood, high in resin and knotted, was not a good raw material and did not yield much profit. Moreover, unlike in its original habitat, it grew too densely here (due to lack of thinning), so where some herbaceous plants existed, they disappeared from the darkened soil layer – along with numerous wildlife species.

Our winding path initially passes oak-mixed stands, later bordered only by conifers. This is a transitional state, as forest growth is slow: what Dévényi began in the 1950s will be completed by today's foresters in coming decades, when pine plantations will be replaced by native species. Occasionally, terrace support structures appear, while at former erosion sites, horizontal plank structures can be noticed – remains of old sediment retention dams.

The frozen bird

The path leads through a warm microclimate, Mediterranean pine forest; at one point, a slippery dolomite gravel path begins to the left. The large monolith of Sas rock needs no explanation – it becomes instantly clear as it emerges from among the trees. The formation of this colossal dolomite block dates back to tectonic movements cutting the Budai Mountains and Pilis, when hydrothermal solutions surged through rock block cracks, cementing hard and durable Sas rock, which erosion slowly exposed from softer surroundings. Climbing the rock is dangerous and forbidden, but luckily unnecessary, as from beside it you can see towards Pilis.

Back to the past

We return to the path and wind until a junction where we turn left. The path leads over a narrow ridge through younger pine forest. Certain pests are especially dangerous to dense, dry, and mixed black pine stands, but severe fires can also sweep through. In 1993, this area was devastated by flames, only contained after 10 days of work by firefighters. In some parts, reforestation had to restart from scratch, while others had enough soil for oak saplings. Before our path slopes steeply down, we get views towards the Kevélyek ridges, and the rugged, steep slopes of Zajnát Mountains also peek between trees.

Though alien and causing ecological problems, the rustling pines create a strong atmosphere pleasant at the edge of the Budai Mountains. Sometimes the narrow ridge shows bare spots where no soil forms on the beaten path, and dolomite gravel crunches underfoot. We reach a saddle with a gravel-filled erosion gully visible with small ditches and broken planks inside, indicating that sediment retention dams still actively work today. Water does not spare the slopes; soil layers are noticeably thin, only patchily covering rock, and trees seem to sprout from stone. The path turns right and soon reaches a wide gas pipeline corridor, where turning left we follow the S trail. Soon we leave the valley to the right and, with about 10 minutes' walk through mixed forest, arrive in the weekend houses of Pilisvörösvár.

At the first junction, we turn left onto the S+ trail, which guides through streets, along a former mining area, to the Szabadságliget railway stop, the pine-bordered endpoint of the hike.