AI compute is becoming the most consequential infrastructure of the century — and today it is concentrated in the hands of a few U.S. hyperscalers. Castellan exists to correct that imbalance: a Swiss-domiciled company building sovereign-aligned AI data centres across Europe and the United States, leased on triple-net terms to the world's most demanding tenants.
More than 85% of the world's AI compute capacity sits under the control of a handful of U.S. hyperscalers. For most workloads, most of the time, that is merely convenient. For governments, defence and research institutions, banks, insurers, and healthcare systems — organisations whose mandates do not permit their data, model weights, or inference traffic to fall under foreign jurisdiction — it is a structural dependency with no easy exit.
The exposure is legal before it is technical. Under instruments such as the U.S. CLOUD Act, providers subject to American jurisdiction can be compelled to disclose data regardless of where the server physically stands. A data centre in Frankfurt operated by a U.S. entity is, in every way that matters to a European ministry or regulator, not European infrastructure. We set out the full argument in our analysis of why sovereign compute is Europe's defining infrastructure question.
European regulation is moving in the opposite direction of the market's concentration. The EU AI Act, GDPR, DORA, and a growing body of sector-specific rules increasingly demand demonstrable control over where models are trained, where data resides, and who can be compelled to hand it over. Workloads cannot always travel. Data sovereignty is not a slogan — it is becoming a procurement requirement.
And the constraint that decides who can respond is not silicon — it is power. AI workloads draw roughly three times the power of legacy data-centre workloads, and Europe alone needs more than €200 billion of AI infrastructure capex by 2032. Whoever controls powered land, grid interconnection, and energy supply controls the pace of the build-out. That is where Castellan starts.
"Sovereign" has become a label attached to almost anything with a European flag on the website. Castellan treats it as an engineering and legal specification: four layers, each independently verifiable — and each of which must hold for the whole to mean anything.
The same stack carries through to the compute layer: tenants who do not want to build can contract sovereign GPU capacity as a service — bare-metal clusters and reserved capacity blocks under the same jurisdictional guarantees as the buildings themselves.
Castellan's build-out is deliberately unglamorous: secure power first, sign the anchor tenant, build, commission, repeat — each phase underwriting the next. The committed pipeline reaches a minimum of 800 MW of sovereign-aligned AI capacity by 2032, scalable beyond it on demand against more than 5 GW of accessible power.
The commercial engine is the powered shell: land, power, and built infrastructure delivered tenant-ready on 15–20 year triple-net leases, in which the tenant bears taxes, insurance, and maintenance and Castellan targets an operating margin near 95% NOI. The intended tenants are the most demanding counterparties in the market — hyperscalers seeking sovereign-compliant capacity, national AI programmes, regulated enterprises, and AI-native companies scaling past the limits of shared cloud.
If your institution needs AI capacity that will stand scrutiny — from your board, your regulator, or your government — the conversation starts here.