10 Highlights of the Thermal Underground Tour

The underground tour is a journey through time and geology. You will walk through tunnels carved into the rock. These paths allow technicians to maintain the spring distribution system. It is one of the most unique experiences in the Czech Republic. Below are the top things to look for during your visit.

• Best Overall: The Vřídlo Geyser Base
• Best for Families: The Stone Rose Workshop
• Best Rainy-Day: The entire underground complex
• Best Free: Vřídlo Colonnade (above ground)

1. Name: Vřídlo Geyser Base Type: sight Why go: See the source of the city's most powerful spring. Best for: Nature lovers Where: Directly under the Vřídlo Colonnade Time: 10 minutes Cost: Included in tour price (approx. 180 CZK) Getting there: Access via the main tour entrance in the Vřídlo hall. Tip: Stand back to avoid the warm mist.
2. Name: Mineral Sinter Deposits Type: sight Why go: Observe thick layers of colorful mineral crusts formed over decades. Best for: Photography Where: Tunnel walls Time: 5 minutes Cost: Included in tour Getting there: Follow the guided path through the main corridor. Tip: Look for the vibrant oranges and yellows caused by iron.
3. Name: The Stone Rose Workshop Type: experience Why go: Learn how the thermal water turns paper roses into stone. Best for: Families Where: Specialized petrification chamber Time: 15 minutes Cost: Included in tour Getting there: Middle section of the underground route. Tip: This is the most famous souvenir process in the city.
4. Name: 19th-Century Masonry Type: sight Why go: Admire the historic brickwork that has survived extreme heat and moisture. Best for: History buffs Where: Older sections of the tunnels Time: 10 minutes Cost: Included in tour Getting there: Located in the deeper parts of the tour. Tip: Notice how the bricks are specifically laid to resist erosion.
5. Name: Aragonite and Calcite Crystals Type: sight Why go: See rare geological formations that grow naturally in the tunnels. Best for: Science enthusiasts Where: Cave-like alcoves Time: 5 minutes Cost: Included in tour Getting there: Guided stop near the mineral outlets. Tip: Do not touch the formations as they are very fragile.
6. Name: The Underground Teplá River Bed Type: sight Why go: View where the city's river flows right next to the thermal springs. Best for: Engineering fans Where: Lower level of the tunnels Time: 5 minutes Cost: Included in tour Getting there: Accessible via the metal staircases on the tour. Tip: Listen for the sound of rushing water beneath your feet.
7. Name: Thermal Water Pipelines Type: sight Why go: Understand how the 72°C water is moved to local spa hotels. Best for: Curious minds Where: Main distribution hall Time: 10 minutes Cost: Included in tour Getting there: Final section of the underground circuit. Tip: Feel the heat radiating from the modern pipes.
8. Name: Historical Drainage Systems Type: sight Why go: See how engineers prevented the city from flooding in the past. Best for: Architecture lovers Where: Side tunnels Time: 5 minutes Cost: Included in tour Getting there: Part of the standard walking route. Tip: Ask your guide about the Great Flood of the 19th century.
9. Name: Petrified Souvenir Gallery Type: sight Why go: View finished stone objects like vases and figurines. Best for: Shoppers Where: Display cases near the exit Time: 10 minutes Cost: Free to view; items for sale Getting there: End of the underground tour. Tip: These make excellent, authentic gifts from Karlovy Vary.
10. Name: The New Distribution System Type: sight Why go: Compare modern stainless steel technology with old stone channels. Best for: Tech fans Where: Entrance area underground Time: 5 minutes Cost: Included in tour Getting there: First stop after descending the stairs. Tip: Check the tickets for Hot Spring Vridlo underground tour in advance.

Planning Your Visit to the Thermal Tunnels

Visiting the underground requires some preparation. The environment is very different from the streets above. Temperatures can reach 25-30 degrees Celsius. Humidity is often near 100 percent. This can be taxing for some visitors. Wear comfortable shoes with good grip. The floors can be slippery due to mineral runoff.

Tours are usually guided and last about 45 minutes. You can find the schedule at the official tourism website. It is best to book your spot at least a day early. This is especially true during the summer film festival. Groups are kept small to ensure everyone can see the sights. Most guides speak Czech, English, and German.

The entrance is located inside the Vřídlo Colonnade. This is the large modern glass building in the center. Look for the ticket desk near the main geyser. The underground is not wheelchair accessible. There are several flights of stairs to navigate. If you have breathing difficulties, consult a doctor first. The air is thick with mineral steam and heat.