Indoor Highline at Be Boulder Amsterdam

We are temporarily closed

Dear SlackNED members and highliners,

Last Saturday, April 23th 2022, an gear incident happened during one of the indoor highline sessions. During a leash fall of the highliner main line failure occurred and the highliner was caught by the back-up line. The highliner was able to get back to the anchor point unharmed but pretty shocked about the situation. Naturally also SlackNED and everybody involved where shocked about this incident. Preventing recurrence of this incident is taken extremely serious.

On Sunday, April 24th 2022, SlackNED started an investigation to the cause of the incident and made an ISA safety report. The conclusion of the investigation is that the mainline whipped against the yellow crane that was above the highline during the leash fall of the highliner. During a leash fall the slackline was launched up due to the tension. The sharp edges of the crane caused the main line to fail. Also the back-up line showed remnants of a collision with the crane. Fortunately it could still to the job it was rigged for.

At this moment all the indoor highlines of SlackNED are closed for this reason. We are looking for a good solution to open again as soon as possible and guarantee the safety of every highliner and those who are present. We hope that with this message everybody is informed sufficiently about the occurrences at the indoor highline.

The SlackNED board

Whaaaaat?! Highline, but indoors? Yep, it’s true!

In the Netherlands, it has become harder lately to practice our ultimate discipline: mid/highlining. We’ve been sent away from a couple of spots, but now we finally got a permanent line in Be Boulder, Amsterdam! 

Under the guidance of one of our instructors, you can practice for up to 3 hours on 2 different highlines. Your line time depends on the total amount of people that are present at the session. There is a maximum of 6 participants, shared over 2 highlines (25m and 41m). 

For this special installation, we have an expensive insurance with all kinds of certifications & a high deductible, for which we need to save money.

Our instructors are volunteers, and we hope to be financially stable enough with the highline to cover their travel costs. 

How it works

To be able to book a session, the following needs to be done: 

  1. Create an account here
  2. Finalize the theory test in the Google Form
  3. Wait for us to enable your account (this can take up to two working days), then book a session
  4. Be able to tie a figure-8 know, show a mantle mount and a leash climb in BeBoulder on the day of the session.
    ⚠️ If you are not able to do those things, the instructor is allowed to decline your participation. You will receive a coupon code for another day.


  1. Always listen to the instructor.
  2. If you fail your theory or practical exam, the instructor is allowed to decline you. You will receive a redeem code after getting in touch with
  3. It’s not allowed to take anything on the line that could fall. So no jewelry, earphones, phones, mp3 players, sunglasses, caps, etc.
  4. Always let yourself be buddy checked.
  5. You can cancel your session 2 days before its start, you will receive a redeem code for another session or get your money back.

Pricing & Booking

SlackNED members & subscriptions holders from Be Boulder get a discount. If you are a member of SlackNED we will apply this to your account. If you are a member of Be Boulder we will ask proof to apply this to your account.

1x Highline Session
Member price: €13,95
Non-member price: €16,95

1x Highlining & Bouldering (€8)
Member price: €21,95
Non-member price: €24,95

10x Highline Pass (valid 420 days)
Member price: €120


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Useful skills & Knowledge

How to leash climb

How to mantle mount (get on the line)

How to nicely fall from a highline

How to handle your leash