A high-pressure/high-temperature experiment based on the multi-anvil technique has yielded a high-pressure (HP) modification of Ca4Te5O14 (I) from the starting materials Ca(OH)2 and TeO2. Reaction with the boron nitride crucible used in the high-pressure set-up led also to the formation of the mixed-valent TeIV,VI borate Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3 (II) as a minor phase. The crystal structures of both compounds were determined by single-crystal X-ray diffraction [I: P21/c, Z = 4, a = 11.0272(1), b = 12.0588(1), c = 10.1038(1) A, β = 91.849(1)°, R1(F2) = 0.0317, wR2(F2) = 0.0459; II: P63/m, Z = 2, a = 9.0890(13), c = 18.731(4) A, R1(F2) = 0.0401, wR2(F2) = 0.0867]. The principal building units of HP-Ca4Te5O14, namely [CaOx] (x = 7, 8) and TeIVO3 and TeIVO4 polyhedra, are similar to those of the ambient modification, but the structural set-up is markedly different in the two structures with an increase in density of about 6.6 %. Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3 is the first compound known so far to contain both oxotellurate and oxoborate units. The most remarkable feature of its disordered crystal structure is the centrosymmetric Te3O6 unit consisting of a TeVIO6 octahedron sharing opposite faces with two trigonal TeIVO3 pyramids. The face-sharing of TeVI and TeIV oxopolyhedra is unprecedented in the crystal chemistry of oxotellurates. In both structures I and II, the lone-electron pairs of the TeIV atoms are stereochemically active.