[4] As the approval process for the expansion faced numerous delays, the latter concept made its way into the existing park for Gröna Lund's 130th anniversary in 2013, where it materialized as the 121-metre (397 ft) tall Eclipse.

In February 2017, Gröna Lund unveiled their 700-metre (2,300 ft) long B&M inverted coaster project, which was set to begin construction in 2018 and open for the 2020 season.

[10] To mask construction during the 2019 season, Gröna Lund created a temporary retro-themed area, stylizing the surroundings to mimic a 1950s traveling carnival.

[3] In late May, the park released a Stranger Things-style advertisement to promote the ride's opening, which subsequently gained a positive reception online.

Facing the waterfront, the train exits the lift hill into a tight curved drop – reaching a top speed of 55.9 mph (90.0 km/h) – and hastily enters into the first of three inversions; a zero-g roll.

The train immediately navigates a Junior Immelmann loop and is followed shortly by a corkscrew inversion before entering a sweeping right hand turn by the park's northern boundary.

The brake run takes riders down a controlled descent back below ground, where they pass through the transfer track and re-enter the station when cleared to do so.

Monster was designed and manufactured by Swiss firm Bolliger & Mabillard, and is one of their inverted roller coasters, as well as the company's first to open since Banshee at Kings Island in 2014.

When discussing the placement of the Monster concept within the existing park, officials summarized that the only way that such a massive project would work was if the formidably sized station and maintenance bays were built underground.