The toy building set comprises interconnectable modular elements that include flat, substantially square bricks, each having two opposite, substantially square main faces, of which a first one is shaped with an array of recesses. Two first, adjacent, narrow side faces bear tabs projecting at right angles from the respective side faces. Two second, adjacent, narrow side faces bear forks projecting from the respective side faces so that the tabs of an adjacent brick can be inserted therein. Each fork is of a size and shape such that it is insertable in one of the recesses with a tight fit. The modular elements also comprise disc-shaped, peripherally toothed bricks, each having transverse openings in which the forks are insertable.