Prominent mine headframe at the active Tytyri limestone mine in Lohja, adjoining a public underground heritage attraction.
Tytyrin kaivostorni is the surface headframe of the Tytyri limestone mine in Lohja, southern Finland, now owned and operated by Nordkalk Oy Ab. Limestone extraction began at the Tytyri site in 1897 when sea captain Karl Forsström founded Lohjan Kalkkitehdas, initially working open-cast quarries at Tytyri and neighbouring sites. The Tytyri quarry served as the company's principal extraction area from 1912 to 1922, then lay idle until 1946 when a new limestone plant was built alongside the reopened quarry.
The transition to underground mining began partially in 1947, when a crushing plant was installed 80 metres below ground. A headframe rising to approximately 72 metres was erected in the 1950s as open-cast working was phased out; surface quarrying ceased entirely in 1956. The mine has continued in uninterrupted underground production since then, with current extraction at depths of up to around 370 metres.
The Tytyrin Elämyskaivos, a public mine museum and experience centre, operates at the 110-metre level and has been open to visitors since 1988. KONE Corporation also uses the mine's first vertical shaft as a high-rise elevator test laboratory.
The limestone deposits of the Lohja area were laid down approximately 1.8–1.9 billion years ago, and local farmers had quarried and burned limestone on a small scale long before industrial extraction began. The industrial phase opened in 1897 when Karl Forsström, a sea captain from Särkisalo, founded Lohjan Kalkkitehdas at Virkkala, initially quarrying limestone from the Tytyri, Solhem, and Hermala sites. Stone was transported to the Virkkala factory by barge along Lohjanjärvi and, in winter, by sledge across the ice. Early extraction at the Tytyri open quarry was modest, but from 1912 to 1922 the Tytyri site became the company's main extraction area. It then lay unused until 1946, when it was reopened and a new limestone factory — the forerunner of Nordkalk's present Tytyri plant, built in 1948–1951 — was constructed alongside it.
Underground working began partially in 1947, when a stone-crushing plant was installed at 80 metres depth. This was reached by a shaft that KONE Corporation later repurposed as a test laboratory for high-speed lifts for skyscrapers; the 330-metre test shaft corresponds in height to a 100-storey building. In the 1950s the distinctive mine headframe — Tytyrin kaivostorni — was erected, rising to approximately 72 metres. Open-cast quarrying at Tytyri ended in 1956, after which all extraction shifted underground.
In 1992 Nordkalk Oy Ab acquired Lohja Oy's mineral operations and has owned and operated the Tytyri mine since that date. The mine works two limestone ore bodies, Törmä and Solhem, and the tunnel network extends more than 60 kilometres under Lohjanjärvi and parts of the town. Current extraction reaches depths of approximately 370 metres. Annual output is in the order of 250,000 tonnes of limestone; the deposit is estimated to have a remaining life of several decades. The mine supplies groundwater to the town of Lohja — approximately one million cubic metres per year are extracted, of which a significant portion is sold to the city as drinking water — and waste heat from the lime kiln is fed into the municipal district heating network, covering around ten per cent of the city's demand.
The Tytyrin Elämyskaivos (mine experience) opened to the public in May 1988, an initiative of the mine's former director Carl Fredrik Bäckström. The visitor attraction operates at the 110-metre level and is reached by a modern KONE lift, installed subsequently to the original shaft equipment. The attraction includes permanent geological and mining history exhibitions provided partly by the Geological Survey of Finland, rotating art exhibitions, and an underground light-and-sound performance in the main cavern. Approximately 16,000 visitors attended in 2019. The Tytyri Hall underground venue seats 100 persons and is available for private events.