MIT’s Computer Science Artificial Intelligence Laboratory (CSAIL) has unsealed a time capsule from the year 1999.

The capsule was created as part of a celebration that commemorated 35 years of research by MIT CSAIL. It was unsealed after a Belgian programmer solved a time-locked puzzle that was created by MIT professor and famed cryptographer Ron Rivest.

Artifacts found within the capsule include:

• The original proposal for the World Wide Web developed by MIT professor Tim Berners-Lee from 1992.
• Microsoft’s first product, the Altair BASIC interpreter.
• A user manual of VisiCalc from 1979, the first spreadsheet program, which later would become Microsoft Excel.
• A paper that laid out the framework for RSA encryption algorithms from 1978 that established modern e-commerce.
• MIT’s 1962 technical paper on “Compatible Time-Sharing System,” one of the first systems to allow multiple people to use a computer simultaneously.

MIT has time capsules all over its campus — some that are buried, others that are hidden and even a few in plain sight.

One of these is a capsule that was placed under an 18-ton magnet in the cyclotron building 80 years ago. MIT CSAIL said that capsule will be unearthed in the coming months as a result of the college breaking ground on a new building there. Another capsule was found in 2015 by a construction team working on a new building. That capsule had been buried for 60 years with the intention of it not being opened for 1,000 years.